sorry mate, but I have to agree with what everyone else has said - she is a whole picnic basket short of the picnic!

Firstly, I have NEVER known a doctor to confirm a pregnancy by writing it on the bottom of a prescription!! (and as you said, in different colour pen to his signature!) If she really had proof, she could get copies of all the blood tests that the doctor would have sent her for to confirm the pregnancy.

Secondly, I have never known a test to be positive with one brand and negative with another, then positive with another IN BIG THICK BLACK LINES! I know all tests are different .... I actually had a case when pregnant with my 2nd child where I had all the symptoms, but I didn't get a positive preg test result until 8 weeks, and even then it was only faint ...

Thirdly, if she does sleep around and try to pin it on you, there's no way she can "backdate" a pregnancy to March! I mean, it's May already!

Ditch her and run far far away!! Take out a restraining order as someone else suggested, but serious psychos don't really pay much attention (I had a crazy neighbour, with the police up her just about every second day ... she even told the landlord that she had rights and couldn't be evicted under any circumstances and that she was in negotiations with local council to buy the property (which wasn't even for sale) ... she was dangerous, as your ex sounds!)

Good luck and steer clear of her!