Sex😥

Alright so I’m 16 and my bf is 18. Lately his dick goes soft super easily during sex. He always has reasons for it like “it’s the condom” which is kinda was cause it was too small and his dick was uncomfortable. So we got new condoms that worked great. But then again he went soft. If we r doing missionary and wanna switch to doggy sometimes he’ll go soft just by switching positions. Today he went soft cause he said my period grossed him out. He just keeps going soft and I don’t understand y. He’s also said that it could be because he watches too much porn or jerks off too much. It’s lowering my confidence cause I worried he’s not attracted to me anymore. Thoughts?