Pre labor bowl movement?

Im due in 22 days and the past days I've been constantly going to the bathroom. Im heavily constipated thinking I really have to go and sometimes its nothing and other times (like last night) it was extremely painful. I was scared to push because the pressure was so intense. Then I went to bed with lower back pains. Anyone else experiencing this? I googled-- says its the body cleansing itself for labor but isn't it too soon? Did any mommies who have had kids exprience bowl movements before labor? Were you dialated? My first appointment to check if I've dialated is this Monday but I'll be calling my doctor today to let him know. He'll ask me to time my contractions but they are not timeable because the pains are mainly at night but I use the bathroom all day!