Very sick boy with RSV

My boy has RSV, has a tooth coming through and had his 12 month needles 11 days ago. He's had a fever for 10 days coughing and is sniffly. This morning he decided he didn't want to eat or drink anything (he's only been having breastmilk the past week) refusing all solids. My MILs approach to this is that he needs to eat or drink something so has been forcefully feeding him small things and it hurts my heart. I keep asking her not to force and her response is she doesn't want him to end up being tube fed so this is necessary. I could honestly cry. She's very helpful at resettling and keeping him calm at night with 39 degree temperature but this is really upsetting me. Is she right? Also, we've been to about 5 different drs who all say these symptoms are normal and it breaks my heart.