Is it ok that my 9 month old can't eat solid food.?

My daughter is 9 1/2 months old and chokes on everything. She can eat some stage 2 food baby food but chokes on even the gerber crawler foods that are suppose to dissolve. I tried giving her watered down mashed potatoes and she chokes on them really bad. I tried giving her cow's milk in a cup (with dr's permission) and is separates her tummy and she throws up the clear stuff and it smells very sour. She spits up the formula almost every time she eats, usually several times. We have tried several different formulas and nothing works. She is losing weight now and her dr and I decided relacting was worth a try before she started any further testing. I just thought by 9 months she should be eating more solids than she does. My other 2 children were feeding themselves crackers and eating table food by now.