Possible miscarriage?

Hello all. I'm new to the forum. In fact, I joined just so I could check on information regarding this topic.
My girlfriend has had a very regular menstrual cycle of 26-28 days since I met her 2 1/2 years ago. She had her last period in the beginning of this month, ending around the 11th. On Saturday, the 27th, she started menstruating again. Is this normal? I know it's not normal in the sense that 16 days between periods isn't "normal" but I've read up on irregular periods happening infrequently and mid-cycle bleeding. I'm wondering, and the reason for this post in the conception part of this forum, is whether or not she conceived and is now miscarrying? She's had all the symptoms of miscarriage except fever. Which are the same symptoms of her normal periods: heavy cramping, abdominal pain, general weakness and overall body hurt. Can anyone give any advice aside from going to the doctor? I would like to not alarm her if possible.

Hi and welcome concerned. I'm sorry you and your girlfriend are dealing with a possible miscarriage. To be honest, my first thought was to check with a Dr, but if you'd prefer not to I don't think you can really confirm a miscarriage or not.

But, if her cycle is always very regular at 28 days, generally she would be ovulating around day 14. I don't know how long her period lasts, but if it's say 5 days, it started on the 6th. She would have ovulated around the 20th. So if you have had unprotected sex around that date, she could have fallen pregnant. To then start her cycle again only 7 days later, it could be a few things. How heavy is it? It could be implantation bleeding, but that's not usually heavy. I guess it could be a miscarriage but I'm no expert here. I wouldn't want to alarm you nor give you false hope.

So, I guess, if it really is very abnormal and she's not feeling well, I'd still advise to see a Dr. Good luck.

Thank you for the reply, Teeki. It's definitely abnormal. The thing is, aside from not wanting to unnecessarily alarming her, she's never been one to go to the doctor. For any reason. Silly, I know.
Last night as I rubbed her feet and asked her about her day, she seemed to be more comfortable, in less pain and whatnot. So, whatever it is, it seems to be subsiding.
Her period usually lasts 5-6 days, starting 21-22 days after the end of her last day. Honestly it's been this way since I've met her. This is the first time she's ever really experienced anything like this since I've known her at least. When I questioned her about it she states that she couldn't remember this ever happening before, but maintains that it is definitely her period. In fact, it's her tendency to be so adamant about this being only an extremely early period is one of the reasons I haven't stressed going to a doctor. I figure a woman really knows her own body and if nothing extreme or emergency-room visit worthy is happening, I'll let it be.
If this does happen to be a miscarriage or implantation bleeding, would her regular cycle resume? That would mean that she would start menstruating on January 1st or 2nd. If she misses that, would that be a sign of anything?