late period

Hi I had a miscarriage in Feb. one app says I'm late by 3 days and the other says two days. took 2 preg tests and both negative. none have been with first urine though. They said 99.9% 4 days before a missed period so I would have thought they would be positive by now. feeling very sick like I'm going to be sick. can barely brush my teeth as Well. feel like I did when I was pregnant in Jan except haven't really got sore boobs at the moment so my question is could I have just obvulated later so my period will just be late this month? very frustrating. thanks in advance