Pain on left side of stomach could this be pregnancy? ?

Pregnancy hormones cause pregnancy symptoms.

If the hormones are not strong enough to show up on a test then they aren't strong enough to be the reason for your vomiting.  

You might be pregnant - you might not be pregnant - but your current symptoms are not being caused by pregnancy hormones - so your current symptoms mean nothing at all.  

Until you get a positive test - those symptoms could be anything and could be more than one thing.  You can have more than one problem at the same time.  (having a stomach virus and PMS at the same time is a good reason for those symptoms.)

Huh? Sharp pains in your stomach, cramping and bleedings aren't signs of pregnancy.  You could have two different things going on:

1. Food poisoning or a stomach bug causing pain, nausea, and vomiting.

2. PMS with is causing cramping, bleeding, and emotional swings. 

If your period isn't late yet or you haven had unprotected sex, then you aren't pregnant.  If you have being engaging in unprotected sex and your period is at least a week late, then you should test for pregnancy.

Periods are not always identical. If you have light bleeding for a couple of days, that's still a period.  There is also a chance that you are having a spontaneous miscarriage.  About 25% of all conceptions end in the first month -- many women don't even realize that's what's going on.

If you are concerned, book an appointment with a ob/gyn who can give you a full exam to rule out other issues, test for pregnancy, and discuss birth control options.