Oh yes, headaches on one side and eye twitching together during the second trimester are more common than you'd think! A few mums I know went through the same thing around 16, 18 weeks, and from what they shared, it's often linked to hormone fluctuations, dehydration, or even posture changes as your belly grows, some had headaches stretching from week 13 all the way to week 20 and everything turned out fine. The eye twitching tends to come and go on its own, but staying well hydrated and resting your eyes more often can help take the edge off. That said, because your headache is specifically on one side and persistent, it's really worth mentioning to your gynae or doctor at your next visit just to rule out anything like blood pressure concerns, better to check and have peace of mind.