Is there something wrong with me?

Early this year I lost my virginity to my boyfriend and it took a few weeks for the sex to finally not hurt and start to feel good with no pain at all since I only see him on the weekends. Anyway the sex is really good but I can never cum, I'll feel like it's about to happen but then the feeling goes away. We've tried different positions, long foreplay, etc and still I can't cum. He's really trying everything to get me to cum and still nothing. Any tips or suggestions on what I or we could do?