Help me set realistic expectations for myself

Hi Ladies, This is my first pregnancy and I'd love some input on setting realistic expectations for what I should expect myself to be able to do. I work a very physical job, and I'm a full time grad student. I'm 20 weeks today, and my OB told me I'm getting to a point where, physically, things begin to change very, very quickly.

I'm feeling intimidated and overwhelmed. I recognize that I'm not very good at setting realistic goals, I just expect myself to always pull everything off perfectly, no matter what. Not terribly healthy or reasonable. I'm working on that, and because I want to work on it, I would love input from others. I don't know any pregnant women here in LA, and absolutely no expectant moms in LA that work a physical job and go to school. It does feel somewhat isolating, but it makes me really appreciate Baby Bumps.

I'm an urban farmer, which sounds like it would be easier than rural farming, and probably is in some ways, but involves a lot of lifting, bending, hauling, strenuous work in the heat (yeah, 90 degrees in Feb sucks). I've always been inclined to push myself hard both physically and mentally, but I was reading today that most women start feeling uncomfortable by 30 weeks, which is not too long from now. My job provides steady, but low income, and my healthcare. I keep hearing from my husband how important it is that I keep it up until the end, but I don't know if it's reasonable for me to expect that I'll be able to. Generally, I'm pretty burned out on this job. I "farm" for obscenely wealthy people in their big yards, but I don't have reliable bathroom access (seriously, I have peed in some very famous yards, and I'm terrified of getting caught). At only 20 weeks, I'm already finding work harder than it used to be.

I'm in graduate school because, for all that's wonderful about growing food in a city, it hardly makes a living. I expect myself to earn money like I real adult (I mean, what other field can you work in for 7+ years, with world class training, and make less than 25k in a year?!?!?!!!), and if that means busting my ass/going into debt for a Master's degree, so be it. It's been hard to uphold my responsibilities and expectations of myself as a student. I come home from work very exhausted these days, and it is extremely challenging to find any energy/focus for school work. Obviously, I do, and some days are better than others. But, I'm not preforming academically like I wanted to.

I'm so happy to be pregnant, but there are some days I can't believe that my husband and I decided to go for it. It sounds like a humble brag, but I'm not used to having hard physical limitations that are sometimes impossible to push past. I don't know how to manage all this, and I don't know what a reasonable person would expect of themselves. Bumpers, I need some perspective.