formula=the devil

In 2 weeks I will unfortunately be returning to work, and with that Owen will be going to a babysitter all day. I have been lazy about pumping enough milk, and my doctor told me I would need to supplement as well to keep up with the chunky little guy. We have tried formula in the past and he sucked it down, the only problem was he broke out in a rash and threw up the whole bottle. So my doctor told me to try enfamil gentleease, I have had it for a week and a half now, being that I didnt want to ruin the nice upholstery on he couches at the beach house I thought today would be a fine day to try it again. I put a blanket down on the couch, I had a bib and a burp cloth ready in case we should re live the great formula debacle of 6 weeks, I made the bottle nice and warm, and as soon as that formula touched his lips he spit it out, and screamed and screamed... and I got frustrated for the first time in 3 months. And that frustraton turned into crying... frustration being frustration with myself, why had I waited this long to try this? I should have listened to everyone when they told me I need to get him used to it, but I thought I knew better... and then the crying came when I thought of him at his first day of day care screaming his head off because I did not introduce the formula as much as I should have. I have had to give him a bottle of formula because of cluster feeding issues and he took it just fine, why is it that all of a sudden he has no interest? As we speak I am sitting in my room, I just got done folding a load of clothes and Im trying not to peak out at Adam feeding Owen to see how its going, Im praying that since I havent heard a peep in 10 minutes that he is taking the bottle... I have mixed it with some breast milk to see if that would make the difference, any advice from any moms out there????