TTC ... frustrated

Getting so frustrated and confused. Been trying to convince. Been trying since the end of last month. Fiancé has cam in me 5 times this month from the 5th to the 19th. Took 5 tests through out the month all coming back negative. So confused on why?? My first 2 kids it took only being cam in once. And found out rather soon.. don't understand why I'm not conceiving.