Denise,
you have what is called secondary anorgasmia. The shocking thing is that about 40% of all woman never orgasm during intercourse. Another 40% cannot reliably orgasm during intercourse. So only a lucky 20% can orgasm every time.
Since you can already orgasm when you masturbate, the good news is that there is about a 98% success rate in fixing secondary anorgasmia.
One of the main reasons why women cannot orgasm during intercourse when it does last long enough and they are aroused enough is that woman have different physical characteristics. In order for your clitoris to get enough stimulation from intercourse alone, its got to be close to the vaginal entrance (< 25mm) - This is the 20% of women. The 40% secondary anorgasmic woman have a clitoris vaginal (C-V) distance > 25 mm. The other 40% inconsistent orgasming woman have a C-V distance of around 25mm or are just lucky to sometimes do something differently that makes them orgasm. This research was first done by Princess Marie Bonaparte, a distant relation of Napoleon

. The rule is called the C-V rule of thumb because 25mm is roughly from the tip of your thumb to your first knuckle
Of course their are exceptions to this, but in general, this is the reason why a woman cannot orgasm during intercourse while she can orgasm by herself (unless her partner is a rapid ejaculator or totally inconsiderate).
During masturbation, you have figured out how you should be touched to get an orgasm, where, how hard, how fast, how deep. Most likely you orgasm from clitoral rubbing, not sticking something into your vagina, or from rubbing your clitoris while you put something inside your vagina.
To get this type of stimulation during intercourse, you can use a special sexual position called Coital Alignment Technique ) or C.A.T.). CAT has a high rate of success (upwards of 87% of secondary anorgasmic women will orgasm with CAT. Even better, these are often simultaneous orgasm with their partners - the holy grail of partner sex. Search the interwebs with the google machine for "coital alignment technique". CAT is ideal for more mature lovers and long term relationships. It is much more relaxed than normal positions.
If you can't find good info on CAT, click on my blue avatar and then 'send a message' and I will help you.
The other technique used is assisted intercourse. You need to find a position where you can get the necessary stimulation on your clitoris during intercourse. This can be you on top where you grind your clitoris on his pelvic bone on the down stroke, or sweep it over his pubic bone on the upward stroke. Or you or your hubby can stick a hand in there and rub your clitoris. Doggy works very well for this. He can have easy access to your clitoris and breasts. You can also get a small vibrator and use that on your clitoris in these two positions.
Another option is for your husband to give you an orgasm before he stick his penis in. For this oral sex is ideal but he can also use his fingers or a small toy. Oral sex and fingering of your whole genital area is ok, he can even stroke your anus lightly with a finger if you find that stimulating. If you have not masturbated for him yet, surprise him and show him how you like to be touched. Men are crazy about that, even though it might feel weird for you.
You can also lay on top of him and grind your clitoris on his penis without him entering you. Or take his penis with your hand and rub your clitoris and your vulva between your labia with his penis head. I think you should get the idea how you can orgasm without full intercourse but still have him close and fully involved in your pleasure.
It is also important to have the correct mental attitude during intercourse. You have to switch your brain off from every thing but sex, pleasure, your husband and any images and fantasies you have. And remember to let the tension build in your genitals and muscles and keep it building.
A good personal lubricant will do wonders. And if you have any body issues, get over yourself. Not one of you are looking the way you did when you were 18. Yet despite this you are craving and engaging in lust and sex. So your pleasure and pleasuring each other is all that counts, not how you look or what he or you think.
I hope this helps you!