For over a year now, i experience severe groin/abdominal/back pain for almost 3 weeks out of every month. what could it be?8 months ago i was told uti.

UTI?: I don't think a urinary tract infection would last that long. Certainly there are cases in which relatively benign infections can become chronic problems however i would think of other possible sources for your problem. Groin pain frequently accompanies hip problems however abdominal pain and back pain rarely occur simultaneously. Your combination of symptoms will require more extensive evaluation.

Back groin pain: If you don't have any urinary sympts such as burning, frequency, incontinence etc., it is unlikely to be uti. The sacroiliac joint in the back can cause back pain(unilateral) as well as groin pain. Hurts more while bending forward, getting up from a chair, climbing stairs etc. Such joint pains increase during premenstrual phase, bad weather, pro plunged standing and walking.