Paint

Ok, i bought this car last fall, and i am having alot of trouble w/ the paint. It has been repainted before i bought it, and it is the worst paint job i have ever seen, the roof and hood and some of the trunk is very rough because of over spray. Recently a spot develobed behind the passenger door, on the top piece of trim around the window. Yesterday i decided to try to fix it, i bought some 400 grit sand paper, and dupli-color primer and paint (white). I sanded the spot down, and got everything smoothed out, i then taped everything off. As soon as i started spraying primer, paint started lifting off the metal, and bubbled up around the spot i was working on.

I was forced to scrape it all off with a putty knife, which wasnt fun. I have been working on simply sanding the entire peice of trim down to the metal, and i will try it again.

Now today, i went to wash my car, and another spot appeared on the top of the trunk.

I am at a loss for what to do, im tempted to get the entire car repainted, but that will be expencive (I can affort it, but there are other things i would like to buy.)

Any ideas?