It can take a few weeks until you are able to stand upright, everyone is different. Try and be patient and let yourself heal, don't push it. Speak to your surgeon and see what their advice is.
10 days post-op form a mini tummy tuck and still can't walk straight?
I'm sorry to hear about your difficulty standing straight up, but don't despair, it can sometimes take 2 to 3 weeks for the tight feeling to resolve. Check back with your surgeon for their suggestions for standing straighter, but give things time to heal and settle. Best wishes, Dr. Lepore.