when can i test for pregnancy???

[Dollymay]

i have been trying to concieve my second child with my husband, and im extremly impatient playing the waiting game! my cycles over the last two months have changed from july being 33 days long and aug being 28 days long, ,so my last period was the 27th of august and it lasted two days, if i was to assume that my cycle was 28 days long like in july i shud have ovulated around the 10th, we have been having sex around those days, assuming that it was my most fertile time, i did a test 2 days ago and it was negative, did i test to early? iv been experiencing back pain on the lower right side, also my face and back have broke out in spots, andi had the king of all mood swings this morning, also been experiencing headaches,when do you think i shud test???i have been experiencing some nausea but i have been told that this cud be attributed to the prenatal vitamins iv been taking, and i took the same tablets with my son and never experienced nausea, all and any advice appriciated, thanks ladies!!