First, it is important to see that this is completely understandable. Contrary to the notion in pop culture that a larger too is better, the truth is that many women struggle to enjoy intercourse at all, and actually find that a larger penis is even more painful and less pleasureable.
Here are some suggestions: first, you don't have to climax via intercourse. Many women really don't. They need manual stimulation of the cliterus. This is really quite normal, and perfectly okay. Ask your husband to touch you there at the appropriate time.
Next, it may well be that you are beginning intercourse well before you are in the mood. Given that men tend to charge up sexually much more quickly than women, and that they want to begin intercourse very quckly, this is not unusual.
Ask your husband to spend time in foreplay. Have him help you get in the mood with hugs, kissing, and light petting. See that you are taking your time as you move forward. Allow yourself to not feel rushed so that you can get in the mood.
What may well happen is that you find your vaginal naturally lubricating. That will help to make intercourse more enjoyable. You may also want to try some other lubricants.
If it is still painful, it is important that you realize this is not so much your fault as it is a natural issue that couples struggle with. Discuss with your partner how you both can get what you need. Perhaps he can enjoy intercourse for a while, but not too long, and he can also stimulate your cliterus in other ways so that you get full enjoyment out of the lovemaking.
Many of the junk out there in pop culture about large penuses being more pleasureable and women that are ready for intense sexual intercourse at a moments notice really are not true. They are the creation of men's fantasies more than anything. Taking it slower, getting in the mood, and being realistic is a big help.