Your blood tests were probably for Rheumatoid Arthritis. What you have sounds very much like Osteoarthritis (wear and tear) on the joints. (Your job would have contributed to this). I suffer from osteoarthritis and have all the symptoms you describe. The fact that your joints are worse in the morning and have to 'get going' points to osteoarthritis. I can hardly walk when I first get up and going down stairs is virtually impossible
I would make an appointment with your GP to discuss it all again. He will probably send you for xrays and prescribe you anti-inflammatory tablets.
There are lots of things that can help with osteoarthritis, but in my opinion the best thing is to keep as active as you can. I have had osteoarthritis since I was a teenager!
However, before going into any further suggestions, you must get a proper diagnosis.
Good luck to you.