Could the side effects of pregnyl fool me into thinking i'm pregnant?

Yes: Pregnyl is hcg, the pregnancy hormone. Yes, it can occasionally cause symptoms that duplicate a pregnancy. Since it is most often used near ovulation, some two weeks before symptoms of pregnancy would appear, those symptoms do not usually confuse diagnosis of a pregnancy.

Sometimes: Pregnyl is HCG which we use to trigger ovulation. Hcg also stimulates the ovaries to produce more Progesterone and the side effects can be similar to pregnancy. A blood test for pregnancy about 12 days or more after the Pregnyl injection should detect pregnancy and not the hormone injection. Eventually, you will have a menses if not pregnant. Hope this helps, best wishes.