I think it's a bit crazy that people start off with rice, and other cereals first. Rice constipates. Carbs set up a person for carb addictions their entire life. Then they say bananas and apples. Good choices as far as them being not very likely for the child to be allergic to them, but gosh...they stop a person up. Remember the BRAT (Bananas, Rice, Apples, Toast) diet is what you eat when you have diahrhea to clog you up. So...I would suggest just try small amounts of veggies to concentrate on.
Here is a good website to find out what to give your kiddo and when:
It is super easy to make babyfood. You can watch the quality, and cut the fillers.
I think one issue that you are dealing with is the timing of the switch to formula and starting food at the same time. Your baby went from the most perfectly, easily digested food in breastmilk. To something that is not as easy to digest that lacks some elements crucial for good absorbtion. On top of that starting food at the same time.
I would suggest taking a couple of days off and just have your baby on formula. It is a balanced meal and your child won't be lacking nutrients. Hydrating also helps push food through. Then just a wee bit of veggies 1 time per day and see if it is all easier to push on through. :)