Is the weight gain due to pregnancy or something else?

Patient: I’m 17 years old and I’m worried that I may have accidentally gotten pregnant. I gained 5 lbs this morning and my weight normally does not fluctuate that much. I haven’t eaten anything this morning either. Me and my boyfriend used condoms but I feel nervous that something may have went wrong. I normally weight 81 lbs and I weighed 86 lbs when I checked the scale. My last LNMP started three weeks ago.. am I pregnant?

Symptoms: Weight gain