^Avna, I love your solution :)
As someone who has had a long term knee injury that I finally got surgery for fairly recently- unless there is an actual injury (and there's not too much to injure there, plus I think you would know if you injured it) the pain is likely weakeness related. As Avna said your solution (and do check in with a dr) is PT. You don't need to necessarily go to a therapist if you do the right exercises. Your goal is to build up the muscles as much much as possible because they likely aren't doing the amount of work they need to be and other body parts that should not be are taking the strain. Your weight is likely hurting, not necessarily causing the problem but you can look up the calculation, every extra pound is something like 4x weight on your knees and 6x on your hips. I know for me with the horses there's a HUGE difference between just walking and walking while carrying a water bucket or something. Riding may be hurting, it may not like the weight I doubt it's the culprit. If it feels ok during/after riding I would keep on going, just try to be aware of it.
Now that my injury is fairly healed I'm working on the same thing, over a year of uneven use has done a number on me even though I was fairly active for most of it. Even if there is an injury which is possible though it doesn't sound likely the advice will be the same.
Good shoes are important. I'm super picky with shoes regardless of any injury lol. I would NOT use a brace unless the doctor says so. It's like wrapping a horse, using a brace will further weaken the muscles which will make the problem worse. While I did use a brace at times I was told it wasn't necessary for me, and I had one doctor offer me an actual brace IF I wanted and others tell me not to bother. (I did buy a BoT compression sleeve, but not the same as a real brace). One thing you can do is my physical therapist started taping my knee recently. That will NOT effect the strength, while a healthy person shouldn't NEED to do it it can be done 24/7 if need be and won't cause any problems (she said she always tapes if she's running or something herself just for the extra support). It made a HUGE difference for me.
And take it easy but also look up GOOD things you can do to strengthen the muscles and relieve the stress on other parts. Don't baby it. I caused my own injury because my knees were hurting (bad build and overuse, as I'm explaining the solution would have been/is to build up the muscles, there isn't anything clinically wrong with me knees) and I stood up awkwardly TRYING to "protect them". Yeah just do things normally. If it hurts don't do it.
How old are you if you don't mind me asking? The general protocol is the same but the older you are the more possible it is you do have an injury without having any specific event, it also factors into what a doctor will do about it.