Opinions on whats wrong with my girlfriend

Ok ill try to make this brief... my girlfriend and I had sex a little over a month ago while she was on her period (she didnt wanna wait because she was going on vacation the next day) anyway we did it and she ended up getting a SEVERE uti having to go to the hospital, get meds, and then rest... all this happened two days after her period ended. she gets back and is getting a little bettet but her diet changed a bit ok so I googled like any concerned guy and a lot of pregnancy stuff came up so I kinda stressed a bit... then two weeks after all that we did it again but twice in one night and yes we get a lttle rough...( let me make this perfectly clear though each time we did it we used a trojan... checked it before I put it on, after I put it on, and after we were done and I pulled out before "my time " so there wpuldnt be any chance each time the condom was good and NOTHING touched if I was unprotected!) sow we do it twice in one night and when she gets jome she is bleeding and that goes on for 3 or 4 days and then stops... the only thing that halfway changed was her getting a few off the wall food cravings and she was really horny like esp during her ovulation, she got a little nausious and had urinating problems but the docs said it was from the uti...oh yeah and now in the last few days her boobs have gotten bigger...and she threw up yesterday morning which I can understand I mean heck I havent had any appetite either!! well we just let it go and we stayed positive because we were very safe!!! ok well 3 days ago she was supposed to start her period but didnt... so she goes and gets a test and it comes back negative... we wait and I do a little googling and last night I bought her two First Responce Brand tests like $10 apeice and she takes them both still negative.... well we feel better because of the tests but why hasnt her period came yet? I read several things about stress being a factor is this true? she has been under a good deal of stress ( arguments with my mom, her dad buying a boat instead of helping with her tuition and making her have to handle how a 18 year old girl is supposed to get college tuition money plus other expenses... then her job making her work crazy hours just because they can ...and then a little stress from being late by a little I mean very stressed!!) and then plus she had such a severe uti right at the end of her last period and then meds and all that... so cpuld that have an effect on her period... I talked to a very close friend and he said he had a very similar experience and took several test which all came back negative and she didnt start until TWO weeks after her regular date... I told her dont stress and if I needed to id buy more tests please help I dont think she is pregnant but I want to know why shes late is it stress or from where she was sick right after her period or is her body just changing because she just turned 18 or what if you need any more info please ask me and ill be happy to inform you thanks for your time!!!
Asked Jul 18, 2014

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