Painful sex

So the past two almost three months when my bf and I have sex its painful it started of manageable by changing position or more lube or my foreplay but the past three weeks its not manageable so I went to a GP and he just did an std check and it came back clear and then said there is nothimg medically wrong and suggested use more lube but the first visit I had told him we already had tried that and if wasn't working even brought a second type incase that worked and it didn't. Is there any advice anyone has that could help?