Yeah I mean you're not on probation, and you've been there for quite a while! And I don't think you have to be 25 weeks. You can be 4 weeks and still tell them. I'd pull my boss aside and mention it! Just let them know you're still interested in working your normal hours, if you have any concerns about heavy lifting if your job requires any of that. And just make sure you know your options as you continue along with your pregnancy. It'll make it a lot easier on yourself. They can't fire you it's illegal.
I been at my job three years so they should be understanding
I tthink you have to by 25 weeks.
Depending on how your bosses are I'd say the sooner the better, that's just my opinion but not everyone has a nice understanding work environment. Lol