Reoccurrence fear

I was diagnosed last December with early breast cancer,then had surgery,radiation now on tamoxifen.my doctors said I have a good prognosis ,I had multifocal stage 1 ,3 tumours. I found doing treatment you just get on with it, but now finding it hard to move on ,have moments of great panic about it coming back or if it has already spread or sometimes I feel like it's just a matter of time before it comes back.  i hope with time this eases.