I get the contraceptive injection every 3 months but then i was on my period for 5 weeks which isn't normal as i haven't had a period since having the injection so now i have it done every 10 weeks, but now i see/get blood clots in my underwear and i don'

Common problem: I always say you either LOVE the shot or you hate the shot--no happy medium. Love it if periods are non existant, or very light & infrequent. Hate it when you bleed heavily & unpredictably. Make sure your thyroid is normal, and, if no better, you may want to consider change of contraception. A Mirena (levonorgestrel) has no estrogen and has fewer bleeding problems, but there is no PERFECT method :-(