Hello, I have gone through your query and understood the concern. If you have always had regular monthly cycles, in the current scenario, your chances of pregnancy are high. You can get a home pregnancy test done now with a fresh early morning sample of urine and plan further management with the help of a specialist. Your symptoms are likely to be seen with a very early pregnancy, but, weight gain is unusual. If the test is positive, please follow it up with a trans-vaginal sonogram to locate the gestation sac and the age of the pregnancy. If negative, you could be experiencing transient hormone imbalance and need a kick-back to the ovaries. Hope this helps.