Literally terrified and sex don't belong in the same sentence, let alone the same bed. You don't need to make a declaration today that you will never feel comfortable enough with your body or someone else to have sex, but you are well within your right to make a declaration today that you aren't ready. Wake up tomorrow and if you feel the same. Guess what? Declare that day's a no sex day too.
Sex, at first, can be intimidating. It is often met with cautiousness and shades of fear, but those feelings of trepidation should not be front and center. If they are, it's our body and mind telling us to slow the F down. And walk away. Give a handjob or go see a movie. I applaud your dude for not pressuring you. Take his lead. It's time for you to do the same.
Think of "losing virginity" (as I've written before) as an opportunity to gain sex. Not lose something. That is the mentality of someone who's on the precipice of having sex for the first time. Whether they love every part of their body or not, is not the deciding factor. Rather, it's the overall sense of comfort with themselves and comfort with the situation.
The decision to have sex isn't built in a day. It's the accumulation of past experiences and sense of sexual, emotional and physical maturity.
OP, you also should look into why fear having sex. Though not PC to say this, but fear on a level of feeling terror of having sex isn't normal or healthy. Nervousness, apprehension, certainly, even a little fear, are normal, but not to the point of being terrified.
Sex is normal, natural, and how we all got here. Try to get comfortable with the idea of sex. Go at your own pace, and realize your BF already likes you for you, and is being decent enough by not pushing you.
It sounds like you're putting more pressure on yourself than your partner is! Calm down. You got into this by over-thinking it, and you can get out of it by not thinking about it at all. Stop thinking about rushing yourself past your comfort zone, and focus on moving at a pace that you do feel comfortable about physically, mentally and emotionally. Sex will happen when it happens. And you will definitely know when you're ready.
If it doesn't feel right, don't do it. Maybe it's not fear of sex, but some feeling that it's not the right time/partner/ect to have sex with.