I'd like to have sex doggie style more often with my husband because I know he loves it so much, but I find it quite painful sometimes. Why is this? and is there anything we can do about it?
It is definitely a position that goes deep, so is likely to cause discomfort at times, particularly if you aren't in control of the thrusting. I suggest that you ask lubby hubby to slow down a bit and permit you to take more control of the situation, particularly in the beginning, and until you find a depth, a speed and an intensity that you're comfortable with. Ask him to stay completely still while you move yourself backwards or forwards until you find the right spot. Sometimes a slight shift of things helps, or a slight angle alteration.
I'm not sure if you use lube or not, but I'd suggest giving it a try. It really helps to make sex smoother and more comfortable. We tend to feel more turned on because we feel wet and we are better able to relax and enjoy it, as a result. It could be, in this case, that you're tensed up and not truly letting yourself go.
Pay attention to the pain, though. If you feel, at some point, that it is worthy of telling your doctor about, you should. It's better to be safe than sorry.
(And might I also add how nice it is that you're wanting to do something FOR HIM, despite the fact that it causes you some pain.)
Have a juicy day!