If it's the problem I think it is, then it can potentially get worse, yeah. The crank-bearing unit could continue loosening, with various ramifications. When you get a chance, put up some close-up photos so I can see what type it is.
By the way, most bike shops would charge between $10 and $20 to get this handled, and you can ask them to assess it and give you a price estimate before you have to commit to having it done.
+1
When I said take your bike into a shop and get a bottom bracket overhaul (or
bottom bracket reinstall may be better wording),
I didn't mean to scare you away.
What they need to do is put your bike on the stand, pull off your cranks and bottom bracket.
Then, its putting it all back together with the right wrenches and torque, bit 'o lube....:huh:
Just be real nice and they'll work with you.
Ask them to snug up your pedals if you haven't already,...they both tighten toward your front wheel....nothing crazy here.
~ If you say its impossible to take your bike in, either you burned your bridges at every bike shop in your area,....or,.....