How to keep baby from getting sick

Okay so my girl is 3 months and she sweats SO MUCH. At night, we have to swaddle her because she still has the startle reflux and can’t sleep without it. Since it’s been hot, she only sleeps with a onesie and socks. My house doesn’t have central ac but in my room we have one. I usually have it set to 68-75 degrees. The air doesn’t hit the baby but today she’s been sneezing a lot and has been having somewhat of a runny nose. I usually turn off the ac when I know I’m taking her out since I know it’s bad to go from cold to hot. Could it be because she wakes up sweaty? I just don’t know what to do. How do you guys keep your little one cool in the summer?