Well Pelin, let's look at each sentence one at a time.
1. I'm glad of my present job.
Is it correct? No. Here are a few good alternatives:
I'm glad to have my present job.
I'm glad to be at my present job.
I'm happy with my present job.
I'm happy at my present job.
Notes: "Happy" can be used in place of "glad". Also, "current" can be used instead of "present".
2. I was unhappy of my ex-job.
Is it correct? No.
Why not? You don't normally hear "... of my job", that just sounds weird. Also it sounds strange to say "ex-job", at least in the part of the United States where I live.
Here are some suggestions:
I was unhappy with my old job.
I was not (wasn't) happy with (or at) my previous job.
3. I was unhappy of my former job.
Is it correct? No.
Why not? The "of" doesn't work here. Use "with" or "at" instead.
Example: I was unhappy at my former job.
I hope this helps you.
Talk soon,
-Cai