Please help TTC😊😓

So I went to get me and my boyfriend some pre-conception vitamins (one-a-day). I got them on 3/09/18 and it’s been two negatives so far💆🏽‍♀️ I’m suppose to get my AF on 3/26, however I’ve been cramping and feeling like my period can come at any day. We keep getting our hopes up but nothing😔 we have sex like Thursday-Monday morning every week. did anyone use this vitamins?👀