Medical weight gain?

Anyone ever have this problem? Since I started taking tamoxifen last December, I have gained 20 pounds. I have been eating the same and it seemd the weight started coming on very quickly. Dieting is difficult because even with eating very little, there is not much change. Weight gain is one of the side effects of that medicine (Along with hot flashes which are nice when the house is chilly), but I wondered if there was anything special I could eat that might help keeping this weight stable and not go higher, I must be careful of not eating too many foods which are high in vitamin K as I am also on coumadin. So if you can't eat salads, what then? Doris