I use Evra patches - for 5 days my stomach hurts a lot, stings and I have a kind of swollen, could it be pregnancy?

If you use contraception correctly - i.e. you apply subsequent patches according to the deadline and in the manner indicated by the manufacturer - I see no reason to worry about the lack of contraceptive effectiveness of Evra. The pain in the abdominal cavity described by you is quite non-specific and may be a symptom of various health problems such as infection or intestinal problems. The use of contraceptive patches alone may cause gastrointestinal side effects such as bloating, abdominal pain or symptoms resembling indigestion. If the ailments do not go away, a gynecological consultation will be indicated. I encourage you to read: https://www.gdziepolek.pl/artykuly/antykoncepcja-hormonalna https://www.gdziepolek.pl/artykuly/jak-prawidlowo-stosowac-antykoncepcje