Hello. I'm 4 weeks pregnant. I have a pulling ache like before my peri…

Hello. I'm 4 weeks pregnant. I have a pulling ache like before my period. I also have a stabbing pain around my right ovary. I had an ultrasound a week ago; they told me to come back at 5 weeks to check the heartbeat. Why am I having this pulling and stabbing pain? The baby was in the uterus on the last ultrasound. And can I take any tablets?