99.6 temp on a 6 week old

6 week old has been congested for the last 2 days. I've been using saline and nose Frida to help with that. Today she sounds worse. Took her temp rectally and it said 99.6. I read I should strip her down until it goes down if it goes up to 100.4 take her to the ER. Is there something i can do right now to help with fever? Ftm and I'm freaking out. I'm trying to get her to breastfeed but she's so sleepy.

I stripped her down and she's still too sleepy to eat