Baby leaning against nerves around your spine...and yes baby also is doubling in size that's where the pressures coming from
I delt with the same exact symptoms you described but around 12 weeks and it lasted about a week, it kinda felt like it would get stuck or hurt to straighten it out and would feel okay when being hunched over. It was near my tail bone in the middle where my spine is located idk if thats the same area that hurts you but i did go to my doctor cause i run to my doctor for every little thing, the staff already know me by my name lol but my doctor said it was normal and it is caused by your spine shifting because its making room for your enlarging uterus and baby...also your center of gravity is being moved so that causes the pressure pain. It should go away soon mine lasted a week
Yes your not the only one try getting a massage I did that an my hip were in heaven your at the stage were the baby starts doubling in size so you will feel but your body will get use to it and you should be fine in a few day try a heating pad to they work wonders