I'm sorry about your miscarriage. Sometimes it's good to wait a full month before having sex without contraception, just to let your body return to normal. Your bleeding and cramping could be related to implantation, or residual effects from the miscarriage, or your body resuming normal cycles and ovulation. Women should always assume that they can get pregnant any time, including right after a miscarriage or even a birth. Everyone is different. Take care of yourself as if you are pregnant, then do a pregnancy test. If you are NOT pregnant, try waiting a month or so (for one normal period) before you have unprotected sex. When you get pregnant again, you want to be in the best possible shape and not be in this state of confusing symptoms. Good luck to you.