2 1/2 weeks after 1st IUI & still a NEGATIVE?

Saturday was 2 weeks after my 1st IUI & i'm now on cycle day 33 but tested again today for the 3rd time since IUI & still got another NEGATIVE result. Usually i do have long cycles so day 33 isn't unusual but i thought from the fertility drugs if i was going to get my period i would of got sooner rather then later this month. Also feel like im going to get my period cause my lower back always hurts every month like it does now. So just looking for opinions could it still be to soon to detect hcg or would i have known by now?? Just have a feeling this wasn't my month once again. Thanks & good luck to everyone else as well.