Pains in my stomach - I'm a little scared!

I'm 23 years old, and I think it's important (before I go any further) to mention that I'm emetophobic - utterly, deathly afraid of vomiting... Therefore, I have a bad habit of mistaking even the slightest discomfort in my stomach/abdomenal area as a sure-fire symptom of the stomach flu or food poisoning... That being said, I'm experiencing pain in my abdomenal area more so than I have in a very long time - I don't believe I'm imagining things, and I'm trying to keep a clear head about it, but I don't know what it is!

It FEELS like muscle pain - On both sides of my abdomen, just beneath my ribs, stretching down to my pelvis... It's also beneath my ribs along my lower back, and a little bit surrounding my belly button... I can't feel the pains when I'm sitting (or standing) still, and I don't feel nauseous, but it's very stiff and painful whenever I move, and it's difficult for me to stand up straight... I haven't done anything that could cause the muscles to stiffen that badly, other than a few sit-ups I did after stepping out of the shower (which I do often, and has not caused this kind of pain in the past)... What could this be? Does anyone have any idea?

Could I be sick with a stomach virus?

If it were a stomach virus, you would definitely feel nausea and all the other symptoms would be more severe. You would suffer from diarrhea, probably vomit (sorry to say), have stomach pain and you would be very tired and exhausted, you wouldn’t feel like getting out of bed, and you would be miserable for a few days.
Stomach virus makes a mess, does its thing, makes you feel awful but it stays for up to seven to ten days but usually around three days.
Considering you have had the problem for a long time, it would be wise if you saw a doctor for a proper evaluation and possible a treatment.