My boyfriend thinks Im Cheating

I have been with my boyfriend for almost seven years and our sex life has been great. We had been mad with each other so we hadnt had sex for three weeks. When we were having sex after the three weeks he sbruptly stopped and said that is was loose and it had never felt that way before. I know I havent had sex with anyone but him in seven years. I dont know why it would be loose. I even went to have a pelvic exam to see if it was a medical issue. Can someone help me.