So so so fed up......... :(?

been trying now since feb when i had my copper coil removed periods been slightly irregular since my last period was august 17th so i should be due tomorrow by rights but i did a Tesco HTP and came up neg on monday so i just think its another FAILED month i just feel so s**t im scared i wont be able to have more children i have a 4 and a 3 yr old and im still with the same partner they is 18 months between my boys so conceiving them wasn't that long at all so why now? im just terrified this is it now im not gonna get pregnant again and i just long for another baby. help please girls