Could my drug regimen of depakote, omeprazole, percocet, calcium, and vitamin d be causing constipation?

Yes. Constipation is a known side effect of both Percocet and omeprazole. If you must have these medicines, increase both your water and fiber intake, and consider adding probiotics to your diet to offset the effects.
Yes. Especially the percocet. Many analgesics and/ or narcotics affect GI motility resulting in constipation.
Constipation. Any of those is possible in combination. Most offending agent of those is the narcotic percocet.