I love my boyfriend but he doesn't last very long in bed..

I've been with my boyfriend for 4 years.. But we broke up for about a little less than a year, and I had sex with someone else during that break up. That person gave me the sex I've never had with my boyfriend. My boyfriend tries to last longer and he tries pleasing me by cumming again and again and again.. So we have sex about 4 times a night.. But it just doesn't happen for me. I can't reach climax with him. As soon as I'm starting to feel good he cums and we have to stop. How do I help him last longer? Please help.