I think its normal to feel some pain for the first couple of times but it shouldn’t be that bad that it makes you cry. You should definitely think about going to the doctor. I can’t speak for how relaxed you were only you can know that. If you don’t think you were relaxed enough you might try again. Also its possible your boyfriend might be really big?
It’s up to her. Talk together, try and figure out what she is most comfortable with.
Girl on top gives good deep penetration and she can control it better from that position as well. But i think girl on top might be a bit intimidating for a virgin. I think when that moment finally comes for you two to have sex you need to be very gentle and slow and ask her what she is comfortable with. I know you want to impress her but suggesting different things the first time might make her feel pressured and anxious. Usually sex for the first time is not amazing, for girls at least. It will take time for you guys to move into other positions. So just be patient with her :) More advice I would give you for her first time is make it all about her, touch and caress her, play with her boobs and nipples if she likes that, play with her clit, make her feel as sexy, relaxed, and as good as possible before you penetrate her. Hope this helps :)