Very bad little lower back pain

Patient: I haven’t done anything too serious, like heavy lifting or anything, i occassionally lift my nephew (who is kind of heavy) and stacks of books at work. I’ve been experiencing a little bit of back pain here and there the last couple weeks, but it usually goes away. At one job, i’ stand a lot and at another, i’m usually sitting for the whole 8 hour shift. I woke up the other day and the pain in my lower back was so bad i had trouble walking up and doen stairs and bending over. the pain hasnt been as bad as that first day , however it still hurts, at times quite badly. i’ve taken some over the counter medicine for back pain and tried heating pads, neither seems to be working. it even hurts to sit down properly. What couuld be the problem? SHould I see a doctor?