Calling in sick to work

I work in Canada in hospital in a job that is unionized, I have many hours of sick time that I am able to use. I’ve was off sick for the past 2 months and just came back to work this week. I worked 2 days and then today woke up with a migraine and had to phone in again. Now I’m stressing about losing my job. It’s very hard to get fired from where I work and I don’t know why I’m stressing so much as I know the likelyhood of losing my job is like 1% but I can’t stop worrying and wishing I would have just went in. Does anyone else work in a unionized job and has experienced having to take a ton of sick time during their pregnancy? Have you run into any issues?