Not Interested and I Don't Know???

I've had two guys ask me out and both times it has happened I get this awful anxious feeling and really don't know what to do except turn them down and then I feel better.

I don't know what the problem is. I don't know if I'm asexual because porn isn't bad but the thought of myself having sex is... Something I don't even know if I ever want. I don't know if it's because I might be demisexual because I think I could date a guy I knew.

- I recently came out as welcome to experimenting with being bi, but that doesn't really matter if I can't even deal with the idea of being with the two guys who asked me out, because there's no way I could get the courage to tell my extremely conservative parents.

Is there anyone who can just give me a hint or their own experience or something?

- I don't know if this makes any difference, but I've never had a crush. Guys, and occasionally girls, have been cute but it's not like it's been anything beyond 'Oh that is a nice look'.

- I'm just over 15 and a half (permit age in my state, yes I have mine) and school-oriented. If that does anything at all.

- Could it be that they don't fit my standards because I don't know them very well and I'm just too over the edge of social anxiety to handle somebody new?