Faithful?

I have been in a relationship with my husband for four years before we got married. I just realized he has still been keeping contacts with his ex. Recently, I discovered he bought her a phone and sent her 500 dollars. I confronted him about it and he said he was just helping her out. My question is can he still be having feelings for her? If so, why then did he proposed and got married to me?

Also, he always gets angry when I bring the topic of his ex. And tells me that I make him miserable in this marriage.

I do not know what to do. I will highly appreciate your comments