Pea sized, hard, tender, lumps (5 or 6 of them) in upper abdomen. Some are slightly bigger than others, none of them are movable. What could they be?

Can't tell. If these have been present for more than a few weeks without changing or getting worse, you should see your doctor about it. The description gave us no clue on what they could be.
See details. One possible causes is a panniculitis. This needs evaluation including a ct scan. If there is a concern a biopsy of a nodule can be done.