Pregnant or nah??

hello. i have a question. my app says i start in 3 days. the other day when having sex i started bleeding. yesterday i had sex and no bleeding. im not sure how accurate my app is cuz i just guessed a lot of things. i have cramps, headaches, fatigue, but i also have an iud. but I don't feel my strings. im also constipated. what do you think this could be?? wait 3 more days to see if I start or take a test?