Weight gain 😔😭

So I've gained 7 pounds and now I weigh 149 and it really upsets me. My boyfriend sent me the sweetest message when I told him about it! But I feel like he wants a skinny girl even though he tells me he just wants me. what should I do?? What are best ways to lose weight?? Im 18 and I am 5'2" "this is what my boyfriend sent me"