You are given full and unapologetic permission to have a pity party. This is a hard road for anyone. But I think to be dealing with this at your young age adds a whole other dimension of, crud, why me, why so young. I have 20 years on you and find it hard to accept. So you go right ahead and have your pity party. But then, get up, take a short walker stroll around the house, then sit, ice, and know each day brings you ever so closer, even if in teeny tiny increments to a life with less pain & more mobility.
As for walking with a cane, first make sure its set for the right height for you. That means the top of the handle should be at wrist length when standing next to you standing straight up. Next, always use the cane in the opposite side. Your tkr was on the left, like mine, so the cane should be on your right. Your gait should be, as you step with your left foot, the cane should follow the same path and add support on the right. I educated myself with this about 8 months ago when my bone on bone left knee was so bad I needed a cane to walk at all. Also I discovered the Hurry Cane, which has a very supportive 3 prong rubber tip, thaf swivels ever so little but makes you feel very stable while walking.
Hope your day picks up.