I've been teaching a decade, from Reception to Year 6, currently KS2 and SLT.
I do mostly enjoy my job but you're only ever a small step away from being made to feel you should leave. There are so many sticks to beat teachers with that all it takes is a HT to decide you're too expensive or you don't fit with the school to make your life a misery. I've seen it happen many times, it is happening at my current school. Two, possibly three, have left or will leave this year due to pressures.
You have to really, really love the job and be able to do a good job without wearing yourself out. I'm lucky, I am in a place where I'm only working about 50 hours a week and managing to prove I'm "worth" keeping on. It's half-term now, I'll pop into school today and again tomorrow: mid-year reports to write and marking to do and planning/resourcing for next half-term. It doesn't end when the bell rings at 3pm.
Please, please, go and volunteer in a local school, ask the teachers honestly, have a look at their to-do lists, check how early they get in and how late they leave. It'll give you the best idea without actually being a teacher. Oh, and remember, the training and first few years are often the hardest, if you're children are that young is maybe wait until they're a bit older or you'll spend the next 5 years hardly seeing them.
I'm going to leave school teaching in about three years, I've spent the last three re-training so I can leave. As much as I love it, I want more to life than being ruled by timetables and piles of marking.
Good luck! :)