Well, have a chat with the doctor who prescribed your SSRI. Drug treatment is an inexact science, so it can take several attempts to hit the right medication and dose.

On a more general level, try to break your tasks into smaller chunks, and accept the idea that you are not good at estimation. Start doubling the time you think things will take. This might generate some negative reactions from others, but what's important is how people feel about you on completion rather than at inception. Consider setting up a time tracker on your computer as well.

finally, it takes time to adjust one's thinking patterns. You're not required to be on full throttle all the time, any more than it makes sense to drive everywhere at 60mph. Treat boredom like any other irritation. Cleaning the bathroom is a dirty task. _______ is a boring task. Accepting and ignoring the lack of immediately pleasant quality will cause your productivity to rise and get it done faster. Developing this skill is a task too. I found it helpful to have a catchphrase to say to myself when I am doing something exhausting or unpleasant. It can be as mundane as 'sooner or later this will be over,' or something aspirational like 'The more I do this the stronger I become.' Ask yourself what you'd say to encourage someone else and adopt that.

I lived in the Middle East for years. One learns frustration tolerance (patience) there by design. There are generally no queues for anything in the ME - not for the post office, or to pay the electricity bill, or much of anything else. It's bad enough having to wait when you are in a queue, but what if there isn't one? Find the longest queue you can and get in it (even if you are not attending or buying whatever is at its end). Stay there until you either get to the end, or have to leave. Repeat this whenever you can. You didn't mention exercise but I have found over the course of 33 years of regular physical activity that "lashing out in anger" is a lot harder to contemplate when the body is physically used. Good Luck.