I am wondering if he is married or has another girlfriend? You only see him once a week and you guys go to places where you would only see/meet a limited number of people?

Once a week for five months.....something is going on...time to figure it out.

I had the exact same issue three years ago, and it was awful... six months of dating on weekends and not being included in his life at all. I started falling hard for him (he WAS charming and definitely beautiful... and i suspect, a bit of a manipulative psycopath) and had to end it because I wasn't getting any love in return. I tell you from experience, if he acts as if he doesn't give a shit about you, he really doesn't.

I'm sorry for you, I was in the same situation 3 years ago. It's pretty clear from my experience that if a guy doesn't include you in his life it's because he doesn't really consider you an important part of his life. I know you might find his excuses tolerable, but in the end, if he treats you like he doesn't give a shit about you... he really doesn't.
The best thing you can do is move on ASAP.
He might have fun with you, even like you for real and enjoy spending time with you. But that's not the same as being in love. You deserve more from someone you're willing to fall in love with.

Is the guys even really your boyfriend? Seriously, like have you guys talked about being exclusive? Because the way you describe your relationship, it sounds more like casual dating than anything serious..
Don't invest yourself into someone not willing to do the same for you.Isn't worth it.

Also, the 'busy with work' excuse? Likely bullshit, whether he even realizes it or not. I've used it on a guy before, and funny thing is, I actually liked the guy, and I WAS really busy, which is why I couldn't find time for him nearly as often as he wanted me to. But then I realized.. Oh wait, I actually find time to see my best friends nearly every day. (Obviously friends are more important than a guy you're dating, but still, I didn't need to see them EVERY DAY). Thing is, when you really want to see someone, you MAKE time for them.
(Unsurprisingly, me & the guy didn't last very long.)

Funny. This almost sounds like me, only that I have understood to some degree the kind of lifestyle my significant other has and am not as worried as I was when we were first starting (We were about 2-3 months when I started asking the same question you just asked).

While there may be a lot of couples who go through certain stages in their relationship (i.e. 3rd date great, let me introduce her to my mother), I've also learned there are really some men who take their sweet time to reach those stages for a number of reasons: 1) They been hurt too many times before they really want to take it slow this time, 2) He really wants to focus on his career but damnit he doesn't want to lose you hence "I'm sorry I can't spend more time with you as much as I can but hey, I love you", 3) you can put your own input here. What you need to do is to figure out if you want this kind of set up. True, you can leave and go out the door and restart the process of dating again and finding someone new. The beauty of it all is that you're always free to do so. But do you want to?

I've met my SO's best friend via YM because the wing man's in a different state. Talked to a man in Africa who saved his life using his own cellphone. These are enough for me to realize he's sharing his life with me at a pace he's comfortable. There's no pressure for him, because that's the last thing I want. While I've never met any of his family members, we always talk about them whenever we're together and vice-versa since my family's not in this country.

It's easy for other people to say he's cheating or has another gf or maybe even a wife; but I've learned to stand in my own truth. My man trusts me because despite the distance and scheduling conflicts we have, he has never accused me of anything and knows he can travel without having to worry he's going to lose me. I trust him because I believe he'll never do anything to hurt me. Naive? No. It's simply having the courage to go through this relationship without the common fear of being cheated on and taken for granted. Take into consideration too, work is important nowadays because of the kind of economy we have. It's a propeller for me to stay put and focus on my career as well, especially since later on in the future, we'd want to have a stable family life together. Also, I believe in the kind of work he has (non-profit) that is why I support him fully, and want him to be very successful even if it means that for now, he'll expend more energy in it while I go establish myself and secure my own future with or without his help (hope this made sense).

Talk to your boyfriend, as GBff suggested. Ask him direct questions, but make sure you're ready for the answers. They may not be the kind of answer you'd want to hear (i.e. It would be this way for quite a while, I need more time, Isn't this being serious enough for you?) Communication, like MM said more than once, is the definition of a good relationship. It's all that's left to do when you're broken and confused and questioning. I've been with my significant other longer than you have been, and we are still doing great despite that I haven't met any of his family who's also in a different state (he's met some of my relatives, however).

Hope it works out for you! Good luck!