Recently I was on another site and heard some very implausible claims about multiple O's... I mean as far fetched as Bat Boy and Elvis Spotted in Topeka! In my opinion, a lot of people feel so pressured now to perform like porn stars, or what they read about, they exaggerate... and worse, add to the pressure and end up with Nothing.
A couple of suggestions. If you're not very sexually experienced you might not know WHAT is the best way for you. Some women "O" more often in certain positions, or get turned on enough by different things. (I had a friend who could only "O" if she was on top, and facing his feet because she had an inverted uterus.) You might consider buying a book like the Kama Sutra to experiment with different positions and aids. Or, if you're adventurous, rent a few porn movies. Just remind your husband not to take their fake "O's" too seriously!! Even if you don't "O" right away you'll have a lot of fun trying new things and exploring together.
If none of that works, you might consider being checked by an OB/Gyn to make sure there's no physical reason for the trouble. If there's nothing physically wrong, you might benefit from counciling together, and separately, especially if you have a history of sexual abuse or fear of sexual activity for any reason. As another example, I had a college friend who couldn't "O" because she was phobically terrified of child birth. In her mind, sex=pregnancy=child birth, so sex was not enjoyable for her, no matter how much protection she used.
But the MOST IMPORTANT!!!!! thing is for your husband to let you relax! If you can't relax and enjoy it, it's not going to happen. The more he pressures you because of his unrealistic expectations, the more problem you're going to have. He needs to realize it's the Journey that matters most, not the destination.
He may benefit from being reminded that, for men, sex begins when they take their clothes off. For women, it begins in the morning and ends after the act. Being more affectionate and attentive to your needs, kissing and cuddling, enjoying some quiet time together before going to bed, would help you get in the mood easier, relax more and potentially have more "O's"