You would have to say "I have a hard time expressing my feelings" or "I find it hard to express my feelings"

"I have a hard time expressing my feelings" or "It's hard for me to express my feelings" important: without context, it sounds like you are talking about yourself in general. If you are trying to give sympathy to someone or talk about a sad event, you should say "It's hard to describe how I feel about what happened" so we understand you're upset about a particular event.