Battery replacement

I have macbook pro early 2011, lately I realized that my battery is swelling and I decide to replace it, I did. But unfortunately it does not gave me good performance and interestingly it start to swellen in a very short period of time. So, long story short the trackpad now does not work, i have to change the battery asap. So, what is your recommendation? Which brand should I get? Why apple does not support anymore, do you think apple

support for the sake of brand&customer satisfaction? Shall I try to ask help from

apple? Why its really expensive? How will i know the brand that I will get would be original or not? Thanks a lot in advance