Pmt irritability and BFPs

Hi. Does anyone know if you can have PMS signs and still get pregnant? I get mood swings every cycle at CD21 (7DPO for me) and dos this month for sure but if implantation doesn't happen till 8-12DPO, could you get PMS and then get pregnant? Just wondering if PMS is caused by hormones your body creates when it's "given up" for that cycle or if I still have a chance...