It will hurt to have sex if you are not lubricated either naturally or by using a lubricant gel.
If you are dry, your boyfriend needs to engage in more foreplay with you and touch your erogenous zones. It can take quite a while to get aroused enough to produce natural lubrication. There is nothing wrong with using a lubricant like KY Jelly. He can apply it to your genitals and stimulate your nipples and your clitoris. He can also apply the KY Jelly to his own genitals before penetrating you. Men get dry just as much as women can.
It doesn't mean that you have gone off him at all. Perhaps you could change techniques to make things more exiting and experiment with different positions. Sometimes you may not feel like having sex and getting turned on. This can be from having a stressful day, being tired or just simply wanting to do something different.
Just because you do not have sex every day, doesn't mean that you love him any less.
Have fun and enjoy your life.
It happens. Doesn't have to do with whether or not you are attracted or not. Been in a few sexual relationships where it is wet and hot for months and I just don't get wet anymore. I use a lubricant. It feels like the same thing and you won't hurt anymore. You can find it by the condoms in drugstores. They come in all different brands and price ranges. It has nothing to do with being dehydrated, but drinking adequate fluids for your body is a good thing. Personally, I think it has a lot to do with expectation and excitement. In, that I know how my partner responds to me so well that, even though I love having sex with him, the spontaneous "surprise and newness" isn't there. That's my take on it for myself.
Maybe you're getting tired of the boyfriend. The body knows before the mind acknowledges, sometimes.
Might have something to do with your hormones. Go to a doctor and get it checked out.