Uti symptoms but negative

It has been about a month that I have been having frequent urination and pain in my pubis area. I pee every often. When I pee I just pee little amount and I have to pee again after couple minutes. I have an urge and pain to pee as If I was holding my pee for a really long time. I have done many test but no infection nothing. I don't know what else can it be and I am so frustrated with this pain and frequent urination. I am currently 15 weeks pregnant. Is anyone going through this. ?