I Am Nearly 50, Pre-menopausal. Last Few Weeks My Tummy

I am nearly 50, pre-menopausal. last few weeks my tummy is bloated and bigger, although I hardly eat. I've noticed a fluttering in my tummy. My periods stopped last year. No periods last year I had one period in December 2015 no period since then. Ive had unprotected sex a few times in Jan and Feb 2016 Now Im worried I might be pregnant. I definitely don't want a baby. If Im 24 weeks or over I cant have a termination! Im terrified. I havnt had sex with my husband for 2 years. If he finds out its someone else's Im in trouble. I thought I had menopause. please advise.