Boyfriend bought me diet pills?

So I've been with my boyfriend almost two months when I first got with him I weighed 116 now I weigh 120. We went to walmart the other night and he goes here come here and took me over to the diet pills and says you should tries theses so after reading a few different ones we decided on a pack. But the thing is I'm not fat granted I'm not toned and I have a shape but I don't look bad at all. So why is he wanting me to take them or even change me for that matter?
Boyfriend bought me diet pills?
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