Does sex hurt sometimes?

I have been with my husband for 6 years. Everytime we have sex it hurts in the beginning and he has to go very slow and afterwards I am sore. Sometimes I will be sore up until two days later. Its not a problem with being wet enough because I always wet and recently I have started using lube but it still hurts. I dont have any sti or stds. Are you supposed to feel sore afterwards everytime? Is it supposed to hurt everytime? I would think by now I'd be use to it. I have been with other people and it never hurt. My husband says its cause I'm not relaxed. But I am always relaxed.