Is a girl I used to date pregnant, or is she lying

[Ben1013]

I need to understand how a pregnancy works. A woman I was seeing, who I soon found out had mental issues, said she was pregnant. Here is a time-line of events.
-7/29 we had sex, said she didn't have her birth control in
7-31 she took morning after pill
8/3 She got her period
8/6-7 she was still on her period, I know for a fact
8/11 she claims she's pregnant  (one of many crazy stories I had been given to keep me around)
8/15 She claims she wasn't pregnant
8/29 I receive a sonogram from her with her name on it

Is all this possible in the time I provided? I've read that it takes about 5 weeks before a sonogram would even be performed. I'm kind of freaking out, any help would be appreciated. Thank you for your time.

[AnnieBrooke]

Was 7/29 the first time you had sex, or had you been intimate for a while?  The 8/29 sonogram should say what number of weeks pregnant she was when it was done, or what her estimated due date is.  Are there any dates on the sonogram she showed you?  

If you only had sex the first time on July 29, and if the sonogram photograph was actually from her on 8/29, it would not yet show an embryo.