Need advice - feel like crud at 21w 5d

My first trimester I had horrible morning sickness and no energy. Thankfully that went away between 13/14 weeks, but ever since two days ago I've had no energy, I walk like a snail, I can barely concentrate on my college classes and get notes down in time, let alone FOCUS on any topic. Also I've started having upper back pain that feels like I'm consistently being stabbed with a knife, and two days ago I had an attack of what I think was heartburn, but my back has not stopped hurting since that attack - and I've wanted little to nothing to do with food and I've been consistently nauseous and worn out. If anyone has any advice that could help me out with any of this I would GREATLY appreciate it! I would love to have my 3-days-ago-functional-self back!