Orgasms are different for everyone. Can you make yourself orgasm? Have you successfully ejaculated while masturbating, for example?
Some people find it difficult to reach orgasm through intercourse alone, some people can only climax through masturbation, and some never experience them at all. So, it's pretty normal, what you're going through.
Also, have you every tried resting after an orgasm? Maybe take 10-15 minutes of rest to see if the abdominal pain is related to continued sex, or not.