Help with sex!

I'm new to this whole sex thing, and so far I wouldn't say me and my bf have had successful sex. Apparently I don't get wet enough and that may be part of the problem because we end up having to stop. I have a really low pain tolerance, and last time we had sex it felt like he was hitting my back wall or popping an air bubble.. I don't know but it was extremely uncomfortable. Any positions or tips that may be easy or non painful for me but feel good for him? Or is there anyway to stretch out your V a little? I don't know I need all the help I can get!