If you can afford it, go find a good horse trader (they are out there, but they can be hard to find - I know one if you are in the Pacific Northwest) who will find you a horse to suit your skill level, get in a barn with lots of other people of like riding personalities and get your own horse.
Heck - if you live near me I would let you come out and meet and play with mine. 169 lbs, he wouldn't even know he had a person on his back!
I have only met one person for whom I thought was justified in saying, no I am not going to ride until I lose weight. My husband combined a medical condition with depression and gained 300 pounds. He has been slowly taking it off, but as he currently weighs in at over 500 pounds, he refuses to ride. I can agreee with that. That doesn't mean he doesn't come out and play with my horse and my daughter's filly. He just doesn't ride.
He will drive with me, but I dont' have a workign cart right now.
So, unless you look like him, you are NOT too heavy to ride. The filly in these pics is 14.2 hand arab - 2 1/2 years old. Hubby is 6'6".