4 month old

So my four month old started daycare back at the end of December. And I feel like ever since then it seems like she has been sick. I don't know if this is something that others experience as well but it's so frustrating. Just when I think she's getting better then she seems to get sick again. I've taken her to the doctors for her cough and they say there's nothing to really help her besides a humidifier at night and using the nose frida to get the snot out. It's just so annoying I wish there was more I could do for her... I feel like such a horrible mom for even leaving her at such a young age but I'm a single mother and I need to work to support us both.