question about twins

I know there is no way to tell if you're having twins before a sonogram but the way I have been feeling kind of has me wondering if I am having twins. since I've known about being pregnant at 5 weeks I've had crazy cramps, sore boobs, extremely exhausted and only getting worse, if I'm not eating every 2 hours I'm nauseous even though sometimes the thought of eating makes me want to vomit (no vomiting though), let's see what else....already forgetful and I've gained 7 pounds without overeating. all this at 7weeks 6 days today......thoughts? my 1st doc appt is Tues. can't wait!!