Sleeping issues

My baby is ebf, and she is 5 and a half months old. Before, I would put her to bed at about 10 and she would sleep until 3 or 4 in the morning. Lately, she falls asleep at 11, and wakes up every 10 minutes, unless she sleeps with me and has my boob as easy access. I've heard of the 4 month sleep regression, but could it be 5 months for my baby? I don't want her sleeping with me every night. I have her in her play yard 2 feet away from my bed. Any ideas as to what it could be? This is an issue that has started this week. Thank you!