Catalytic converter or fuel pump?

Ok. 1999 (I think) Blazer, 4 door, under 80,000 miles I am 2nd owner.
A couple months ago, my gas gauge started bouncing around, sometimes fast, other times slowly. I end up running it out of gas. Week or two later, mpg gets worse, truck starts lagging, slowly loosing power it normally has. It begins to act like its running out of gas all the time. I treat gas with high octane racing fuel type shit. Truck runs like before for a about a month. Then starts acting up again. It eventually looses all power, Im on the side of the road. Truck ran hot, but never registered on gauge. But I could smell it. It cools off, starts up and makes it home. I am thinking catalytic converter, loss of power, mpg gas, plus, it has been rattling up under there, and that steady got worse. Had oil changed and asked the guy, he said yes, thats what it is. What I didnt realize until just today, it quit on me while full of gas. I have drove it when it would make the 2 mile trip to the store until it is now under half a tank, I'm back to not having issues. But I can feel the heat coming up the floorboard, thats been happening for a while now. $485 to replace catalytic converter, I dont have that. Also, just an observation, when truck is running bad, my left turning signal blinks very fast, no issues, it blinks normally. (Really?) But the converter is going to steady get worse, right? Not fine a month, then bad again. The half tank gas issue got me thinking, could it be my fuel pump? I am a single unemployed mother of two and a full time student. I moved to a town I know nobody in, and the vultures smell all that. Im not an idiot. But I cant afford to pay a couple hundred dollars for them to tell me thats not the issue! I am 200 miles from guys I trust that could fix my truck. WHAT DO YOU THINK IT IS? Is my fuel pump in my gas tank? Mskris1234@yahoo. Com or 205-657-7530