I don't know about your other subjects, but History definitely won't be easy. As well as essay and source skills - which might come naturally or not, but will still take some getting used to and practice - there's a lot to learn. After starting AS History, GCSE History felt like nothing. After starting A2 History, the amount of content that I had had to learn for AS felt like absolutely nothing compared to what I had to learn then. If you have a good revision technique and you start early, you'll be fine - but don't underestimate History. It's definitely really enjoyable though, and I'm going to miss doing it.