Day 19 and ...need answers

so its day 19 and lets see 4 days past iui counting 16th as day one 15th was iui anyways i am having back ache lower and i am on prometrium u think its because of that and the tiredness it has been worse than ever! i am just exhausted any answers? i mean, i am hoping this is not all from prometrium! and its other things ugh like being pregnant!