Sounds like your valve body has a sticking valve in it. It's not uncommon for this to happen, after a flush, if you have not changed your fluid on a regular basis before the flush. You can check the CD4E FAQ's, in the tranny forums, for some personal insight on this topic.
For what it's worth, if you cannot put any money into it right now, then I would suggest trying a bottle of Lucas Trans Fix (or whatever it's called). It really saved my tail in a similar situation, which I was about 200 miles away from home.
To fix it for good, sounds like you might need a valve body, which can be had for around $250 or so. Again, check the tranny forums, CD4E FAQ and do some searches on "valve body", and you should be able to get all the info you need. If not, please feel free to let me know and I will try to help you out.