Poor Credit! Need A Car! HELP!!!!!?

My car (A Honda Civic) is under my father's name and the lease will be up in June. (I've been paying it though all this time) I'm over the miles, I am supposed to turn it in by 36,000 miles and I am at 50,000. My credit is horrible right now b/c of 2 past credit cards that went into collenctions b/c of deliquency 2 years back (i just finished paying 1 off in october) and I am currently paying the other one off, plus my bank account went negative at the time and i have applied to atleast 10 credit cards since then.. so my credit is horrible.. I need to take out another car in June, how would I go about that? I have 5 months to clean up my credit. Is it possible? DO I save money for a down payment? I CANNOT get a co-signer b/c my father no longer wants to have his name under my car and my mother has bad credit. I was looking to take out a MINI-COOPER... please help!!!!! is it possible to pay off the over-mileage under my name even though the car was under my dads name? HELP!!!!!!!!!!!!!!