Can I be discriminated for UC during a "temporary" position?

I just got hired a couple months back for a temp-to-hire position (3 months sort of probation period before you get taken on as a perm). Around the time of hiring due to stress (I think) I developed a flare. I have taken a 3 day leave due to symptoms to try another fecal transplant attempt after which I guess I'll have to resort to prednisone because I need a quick fix.

My question is.. I took 3 days off and have to come clean as to why (and sort of mentioned I have a stomach flu to my boss. I didn't specifically say I have UC or a disease). I'm thinking of telling my boss I have UC because I think I'll be forced to take more sick time off if this fecal transplant doesn't work. And I'm just really scared they now won't hire me because I was sick during my trial period.

Basically, if I tell my boss/HR I have UC and don't get hired after the 3 month period, can I do something about it? I'm sure right now (have 5 weeks to go before perm) my doctor can write up FMLA or whatever is needed to prove I need/needed the time off. But will that do me any good? Or can they basically not take me on for whatever reason?

Really concerned

Depends on if you live in a right to work state. Here in Virginia its a right to work state and they can choose to not hire you even if you did everything perfect and you have no legal recourse.

Now if you don't live in a right to work state and after your 90 day probation they told you we aren't keeping you because you were sick and late etc thats when you want something from your doctor and possibly legal representation.

Then you have it a little better than I would.

Thanks for the tip. I'll keep my mouth shut :X However I did make a stupid mistake already. The morning I decided I had to take the 3 days off I sent my supervisor an email. In there I said [...] "It would be much appreciated if we could keep this between us and if you could tell ABC and XYZ that I just have a stomach flu (which is not a lie - except what I have is a bit worse). And I will explain it to you on Monday." [...]

I was kinda planning on telling him I have UC (in anticipation of the fact that I'll probably need to take more time off before prednisone starts working once I do start taking it. What can I say at this point on Monday? Do you think it will make sense if I said I contracted sallmonela poisoning? I need to one up the "stomach flu" thing because of my stupid email I sent