Oo, totally normal yan, lalo na first pregnancy kaya lahat ng sensations feel so weird! A few of us in our mum group felt the same tightness around that time, it's usually a mix ng uterus na lumalaki, plus pregnancy hormones making your digestion slower kaya ang bloating at constipation talaga. Try to drink tons of water, eat foods with fiber like ube and leafy greens, at take it easy on the heavy meals, pero if the tightness becomes painful or you're worried about anything else, better check with your OB para sa peace of mind, sis.