can anyone tell me whats going on with me

ok so I'm 22 me and my fiance aren't actively ttc but we aren't trying to prevent it but starting Friday of last week I have been extremely nauseous to the point I have missed now 3 nights at work and was in the er last night I have had 3 urine test and 1 blood test yesterday and all have came back negative I feel the exact same way now that I did when I was pregnant with my son except the nasuea is worse I was supposed to start my period today but nothing we were secretly hoping to find out we were expecting I am extremely emotional and moody the doctor at the er last night said "this might be symptoms of your period about to start if it doesn't you need to follow up with your ob" ok 1.) I have had my period since I was 13 I know my body and my symptoms and this isn't it 2.) if I'm not pregnant why would I miss my period if anyone has any advice please help if I'm pregnant that's fine it would explain why I'm feeling like this if I'm not find out what is going on with me