Posted a while back about this - my sister is now about _8 weeks_ late. She went to the out of hours docs with a virus a couple of weeks ago, had bloods taken, mentioned she could be pg - results have still not come back (her doc surgery is rubbish!!). Anyway, she went to the docs again yesterday as she still feels quite achy and tired, although not unwell as such. She has done about 6 HPTs and have been BFNs. The docs has now said to her that she has to have a blood test tomorrow to rule out pregnancy. She has said that if she is pg it would tie in with a possible conception date. But she is convinced she isn't pg (NB she has one DD aged 2 so she has experienced it before). But what else could it be? Up until now she has always been v. regular.
My sister had a really nasty virus last February, was literally in bed for 2 weeks with it. She took months to recover and even had to go on a special diet as she had not eaten properly for so long, her body could not properly digest the food. Anyway, she did not have periods for months afterwards. She too had blood tests (not pg related) and nothing showed up, was just a virus that really knocked her about. Perhaps it is just after symptoms of the virus? I hope that she feels better soon.
Its difficult to tell, it really could be either, although the virus/illness is more likely.
If she had sex at the right time she could be pg. Not everyone produces enough hcg in their urine to make a pg test positive, only a blood test/scan will confirm. This is however rare, so not that likely but it does happen.
It is however, just as plausible (and more likely) that the virus/illness has simply effected her period. When I was really ill with ME the longest I went without a period was about 6-8 months but I had 2 years with a period every 2-3 months and it has only been the last 12 months that it has been more regular and I have been "well" for 2/3 years. If your body is really ill it stops non essential processes, therefore your period can completely stop.
If she has had a very nasty virus it could easily of stopped her periods. When are bodies are challenged they shut-off some non-essential services to conserve energy and get better. She may now be suffering from something like post-viral fatigue which is horrible and can go on and on.