Hi,
Welcome to the ehealth forum and I am glad to help you out. The hormones produced during pregnancy affect the lower back and cause pain and still other times there are is no visible cause for the lower back pain. It may have got complicated by your ovarian cysts.
The cure for lower back pain during the first trimester and even throughout the rest of the pregnancy is to do pelvic tilts. Another way to reduce back pain in the first trimester of pregnancy is to try and avoid gaining too much weight, wear flat heeled shoes, maintain proper posture, and do best to get enough rest. Lower back exercises like pelvic tilts and others will help strengthen the back and reduce back pain. Please do consult an obstetrician and a physiotherapist for the same. If possible, avoid taking any painkillers for the same and in fact any medication should be avoided during pregnancy. But if the back pain is severe then please take the medicines after consulting your gynecologist.
I sincerely hope that helps. Take care.