Unless you have damage to your nervous system (e.g. spinal cord injuries, diabetic neuropathy), then nope, you can't be physically incapable of orgasm.
However, it can take a while to figure out what works for you and for your body to figure out how to orgasm - it's a bit like learning to ride a bicycle (only usually it's more fun and leaves fewer bruises ).
It's perfectly normal to find that the sensivity of your genitals changes during sexual activity. So when your clitoris gets hyper-sensitive, you could try continuing but lightening up on the stimulation.
Many people also experience hypersensitivity right after orgasm, so it's worth asking yourself if you could in fact have an orgasm.
Sometimes people expect orgasm to be a much bigger deal (with the earth moving, bells ringing, the heavens-opening, and lots of movie-style screaming) than it actually is.
it does feel good doing everything that my boyfriend and I do and would it be silly to just be happy and satisfied with that?
Not silly at all.
Orgasms aren't compulsory, and they're not some special badge of achievement you have to get. They're very nice, but they're not the "goal" of sex.
If you're happy and satisfied, you're happy and satisfied, and that's great. Orgasms are just a nice bonus if and when they happen .
But in a scientific sense why do women need to orgasm?
Actually, it's physically perfectly possible for men (or the males of any species) to ejaculate without the sensation of orgasm. So in that sense, men don't "need" to orgasm any more than women do for reproduction to take place.
But orgasms (and pleasure from sex in general) help motivate complex creatures like ourselves to engage in sexual activity in the first place, so that reproduction can take place.
In addition, in most species of mammal, sexual activity has lots of other functions apart from reproduction - it's part of social activity, it creates pair bonds, and sometimes it's just fun (check out any study on the sexual habits of bonobos, a type of chimp believed to be one of the closest relatives of humans).
So orgasms - and pleasure from sexual activity in general - help motivate all those other important aspects of sex, which help the community and the species survive. It's why it makes evolutionary sense for non-reproductive sex to be fun too .
That's my take on the research, but for a much more detailed discussion of the female orgasm and its evolutionary role, check out Natalie Angier's wonderful book of the science of female bodies, "Woman: An Intimate Geography".