Hey J.,
I was having back aches when my daughter was around 20 lbs... Not sure how hefty your little man is at 14 months... However, my chiropractor mentioned that he often sees a lot of post-pregnancy patients when the baby nears 20-25 lbs. He explained that around the time that the child is that weight, the baby is not primarily walking yet and is still being carried a lot, which puts more and more strain on the mom's back (particularly the lower back). Also, bending over the crib to pick up a 20 lbs toddler strains your back; you're suppose to lift with your legs however leaning into a crib makes lifting up with your legs impossible. And leaning over the changing table is awkward on your back too. maybe you can try changing him on the floor?
My daughter rarely insists on being carried now (way too Miss Independent for mama to carry her!). So, I haven't had those kinds of back aches since she was around 20-24 months. I would suggest that you ice your lower back 3 times a day, 10 minutes for each session. It might be worthwhile to buy on of those ice pads that have velco attachments (to hold in place). They sell them for about $10 at the grocery store pharmacy; that way you don't have to be stationery when you ice it. I know, everyone hates to ice but it is really the only way to decrease the swelling. Heat only makes the inflamed tissues swell. And really, the 'ice ache' only lasts for the first 3 minutes; after that, your skin gets numb to it.
And of course, try to reduce the amount that you're lifting/carrying him. Maybe you can get him to stand up in the crib before you lift him out-? That way you'll lift more with your arms and legs..
Try to avoid taking tylonal/pain killers. Daily use of that medication over an extended period of time will cause ulcers and intestinal bleeding. (Embrace ice instead!)
Good luck. Hope you feel better.