Dola*

I did Biology HL, Chemistry HL, and AP Physics B, and my experience with the subjects was that Physics has some concepts that also show up in Chemistry, and Chemistry has some topics that are also in Biology, but neither is particularly similar to either of the others. Although I had the hardest time with Physics (I somehow managed a 5, however) I believe that Chemistry is the subject that is genuinely the most difficult, but also the most interesting and engaging. For me, Physics and Biology were absolute bores, each for entirely different reasons; Physics because I had a hard time picturing anything more abstract that simple mechanics, and Biology because it all seems very random and as though there is no reason to learn it, and it was also rather easy.

So... If you had a hard time with Chemistry, you might have a hard time with Physics, because there is a fair amount of overlap. (at least there was between AP Physics B and IB Chemistry HL; half the time, it felt like what I was doing in Physics was just review of Chemistry) If I were in your situation, I would do Biology. Probably at SL, because for law you certainly won't need HL, and SL is far easier in terms of how much detail you need to know.