It's a difficult one... the fact that you can make yourself cum, means there is no physiological issue. It also means that no partner has found the key to you yet; and the first key is going to be in your brain. I have had the same problem with most of my partners (but not all, proving that it can sometimes work). I firmly believe the key is that each of you should be open and willing to give pleasure to the other and to receive pleasure from the other: breaking down of the inhibitions. BDSM is a great world for that, slowly but surely, as confidence grows. It's a question of letting yourself go: abandon. It's also a question of your partner persevering and being observant: learning how you tick, what actually turns you on. And being patient.
I have cum on command, to my utter surprise. Not what I'd call a good orgasm, but it has happened. I have found myself cumming just on remembering my dom's voice telling me to cum - pavlovian training at it's most powerful! But mostly, I find it very hard to cum via someone else, and certainly cumming through vaginal penetration is difficult. That is a frequent issue.
One way is to make sure you please yourself. During penetration, your clitoris is not getting enough stimulation? Rub it. Make yourself cum, and your orgasm will be stronger through also being fucked at the same time. This is also a liberating experience: you start to learn to cum with another and through another.
When your partner is attempting to make you cum - tell them what pleases you. Tell them, left a bit, down a bit, don't stop, etc. Yes, this can seem difficult if you are with your dom: so talk about it, ask permission to guide them if necessary.
Listen to yourself. Be aware of your own inhibitions. Be aware of the little voice inside that starts saying 'oh no I can't' when you start moving towards orgasm through another's hands (or mouth or cock or whatever). Oh yes, you can. Even if it's different.
Use toys together. Does a rabbit make you bounce with joy? Get them to use the rabbit on you. And guide them.
There's a barrier to break: once you have cum once through someone else, you will realise you can. I'm not saying the floodgates will open, but it will become easier. And if not, do what love2please does with hubby, at least you get to cum and at least it's together!
One thing I'd like to say: I can never, ever give myself as good an orgasm as I can get (eventually) through a partner, when they get it just right... it totally blows my mind. And if it takes being tied to a door, whipped, breasts clamped and weighted, and being brought to the brink but not fulfilled for a few hours... THEN finally get to cum till you pass out... It's worth it.
But, I certainly don't cum as often as he thinks I do: yeah I fake 'em. Or rather... I make a lot of noise because it IS good - and because it helps me get past my barrier, helps me build up to it. Only sometimes he doesn't judge the noises right and thinks I am already cumming when I'm not, tells me to cum and then I can't but I don't want to disappoint... etc. So, hey - it doesn't work every time. So what? Sometimes I wait till he's gone and give myself a swifty! What I DON'T do is spend hours analysing and agonising over it. This leads only to more mental blocks.
Of course, your partner has to want to make you cum, has to truly get enjoyment from it. You are unlikely to meet that in casual relationships. In fact if you find it hard to cum through another, casual relationships are the least likely path to changing that. I'm not saying I'm against casual sex (I've done a lot of it myself, too) - I'm just saying, they are probably the least physically fulfilling.
Woah. Havn't been on this forum for a couple of years and my first post is an essay!