I just got a new bike. I absolutely love it but i am experiencing lower back pain. The bike before this was a 15.5 and felt that was too big. I couldn't maneuver it well and I felt it was too high, and became squirlly trying to get through the trails. I thought it was my inexperience but after 3 years and still not working out i deceided to try a new bike. I stumbled upon a trek wsd x-cal that was 14.5 and fell in love! I am just at 5'3 with a 26in inseam. this bike so much easier to ride but after riding about 2 miles on pavement, an hour later i started to get pain in the lower back. Now my old bike which was a trek cali sat upright too much and when i raised the seat the geometry was off and it was too high! this new one i feel like im in a normal mountain bike position. Is this pain from not being used to riding like this or is this bike too small? I don't feel its too small. Maybe i am overthinking.