Maybe your joints, tendons, ligaments, etc. aren't ready for that. How long have you been lifting?
Are you taking 1500mg glucosamine? Any less (and no need for more) is proven ineffective. Are you taking your fish oil?
I have been lifting for about ten years. I weight 245 on a 5'10" frame. I take flax seed oil and omega 3 fish oil everyday twice a day. I might have to check and see how much Glucosamine I take in a day. I take three pills a day everyday but don't know the mg.