Hi,
thank you for your question at healthcare magic.
Provided that you did have sexual intercourse, specially on your fertile days, and since your periods are delayed,
pregnancy is always a possibility, if your symptoms are anything to go by.
Even though you took a
serum beta hcg test, 5 days post due date, I advise you to re take another serum beta hcg test after another week or so if you still dont get your periods by then.
The reason for suggesting this is that sometimes our beta hcg levels take time to rise up enough to be detected. Since it doubles every 3-4 days, a re take of the test after a week should give a definite interpretation.
Meanwhile, you should observe caution until you get either your periods or a positive pregnancy test.
Hope this helps with your situation.
Thanl you once again for visiting healthcare magic.