I have been with my boyfriend for 3 years. Every now and then he says that my vagina gets loose. I'm not doing anything for it to change sizes. He thinks I'm cheating on him and I'm not. I don't know what to do. I'm so speechless when he says whats going on, why is it like this. What am I supposed to say to him if I'm not doing anything? And what makes it feel different to him?
You can tell your partner that he's incredibly misinformed.
You might want to check out my answer to another question about vaginal tightness. But the short answer here is that your partner is woefully confused about female sexual anatomy and arousal. The vagina does not permanently change due to penetration or sexual activities. Heck, a baby can come through the vaginal canal and (in most cases) not cause any significant changes to the it...why in the world would a penis cause changes if a baby won't? I don't know about you, but I've never seen a penis the size of a full-term baby!
While permanent changes do not occur, temporary changes to do happen during arousal. When a woman is relaxed and aroused, the vaginal canal loosens and the cervix pulls up to create more room in there. So things feel loose because you're aroused and because that's the way they're supposed to be when you're participating in penetrative activities that you want and are into. If you're "tight," that's a good sign that you're not aroused or that you're not really wanting or ready for penetration.
If your partner thinks that you should be tight during penetration or that you must be cheating if you're not tight, then he's the one that's wrong here, not you. Your body is just responding the way that it should. Unfortunately, we've developed this cultural obsession with a) tightness being a good thing, and b) the state of a woman's vagina as some indication of fidelity. Both of those are completely wrong.
So let you're partner in on the truth. If he refuses to believe you, you're welcome to send him here and we'll tell him the same thing! And if he still doesn't like it, then your best bet is to find a new partner who understands the way that arousal works and wants you to enjoy sexual activity.