Work/FMLA Question

I've been a type 1 diabetic since 13 and I'm now 30. I have been with a company for 9 years and have been considered an employee of good standing for the past nine years. Recently I had a boss that made me take half days for Dr. appts even though I would schedule them at 8am and be in the office by 9:30-10:00am and be on work emails some nights till 11pm. After taking close to 10 full days of vacation for dr. appts I started feeling like my it was starting to reflect negatively on the way I was viewed and I started missing and cancelling appointments. I asked a friend at the company if there was anything I could do and they told me to speak to someone in Benefits who told me I should sign up for Intermittent FMLA which basically allows me to see a Dr. whenever I need to without taking vacation days. I called FMLA and they told me I had to notify my boss's which I did right after that phone call. About a month later my FMLA claim was approved and the week after I received the approval email from benefits my boss changed my rolls to a lesser status and than 2 days later put me on 'goals' which means that they feel that I am performing under company standards and I had 60 days to change that or I would be fired. After 9 years this had such an impact on me that I ended up getting really sick and had to go on short term fmla for a 2 month stint. When I returned to work finally my goals period started but after a month and a half I started feeling like there was nothing I could do to make my boss think I was improving and I really tried hard to be a model employee. One meeting he told me I wasn't interacting enough in meetings than a week later he told me I was too overwhelming as well as I didn't have the trust and respect of our merchants which when my roll changed I hardly have any interaction with anymore where as before I used to constantly. He than said this is how he felt and he was going to let HR know this. This experiance has been HELL for me for the past 4 months and I feel that after 9 years of working hard for this company I'm getting treated differently since signing up for the intermittent FMLA. After a month and a half of notifying my boss's of it, I was put on goals for the 1st time in the whole 9 year period. I've also made it through 2 MAJOR lay-offs before this over the past year. I'm going back to work on wedensday without having any idea of how things are gonna go, but I know this is the first time in my life I feel like my diabetes has controlled me and not the other way around. Is there any advice anyone could give me on how best to deal with this? I don't know if I'm going to be fired or not but it seems like things are going that way. Has anyone had an experience like this?

Any advice or stories anyone can tell me that relates to what I'm going through would be very much appreciated. Sorry this was so long :)