Birth control questions

I just switched from the nexplanon (birth control that is inserted in your arm) to the depo shot. I'm coming up on my third month of being on it and I read online that the longer you're on the shot, nexplanon, or the IUD the harder it is to become pregnant after you're off of it. I want to stay on some form of birth control until I'm done with college(other than the pill), but I don't want it to effect my chances of being pregnant after I come off. My boyfriend and I use condoms, but sometimes we don't but he always pulls out. Has anyone had any problems after coming of birth control? What should I do?