Fat or muscle

So I was 110 and now I’m 114 in a matter of a month. I’ve been 110 for several years and now I’m gaining weight. I only work out twice a week so I feel like muscle wouldn’t gain that fast. Due to working out my appetite has also increased but I also started birth control about 3 months ago. I know I have weight to gain but I’d like it to be healthy weight gain. Any thoughts? Not sure if it’s fat from eating so much or muscle. Thanks