FIL treated me like a maid on SIL’s moving day, and I can’t shake this feeling of isolation.

⁠Hi, I’m here to get your advice. Please hear me out. Before this happened, I genuinely had no problems with my in-laws. But now, I don't know how to fix or process the feelings I have.
Last Saturday was my sister-in-law's (SIL) moving day. I was more than happy to help her—zero problems with that at all! We were moving boxes and unpacking everything at her new apartment. Suddenly, my father-in-law (FIL) called me over and said, "I have a job for you." I went over and asked what it was, and he pointed at mold growing on the window frames and told me to wipe it off.
My husband was visibly taken aback and immediately said he would do it instead, but in the end, I ended up doing it. While I was cleaning up the mold, neither my FIL nor my SIL lifted a finger to help with the cleaning at all. Instead, they just stood there together and asked if I needed a mask or gloves. It felt so hypocritical and condescending.
I just keep questioning this: It’s my SIL's new place, is it right that I was the one cleaning up mold? I am more than willing to help move boxes. But I am also a precious daughter to my own father. It felt like FIL didn't want his own daughter’s hands getting dirty, but it was perfectly fine for mine to get dirty. Am I being too sensitive?
I was so heartbroken that day that I cried the entire evening. My side of the family lives in another country, so the only family I have here is my husband and his relatives. Being discriminated against like this makes me feel like I’ll never truly belong to this family—it just makes me feel like a maid. Because my own parents aren't here in this country, the sorrow hit me even harder and the tears wouldn't stop.
When we got home, my husband kept apologizing. But honestly, it’s not my husband who did wrong; it’s my FIL and SIL. I genuinely don't know how I’m supposed to face them or look them in the eye moving forward.
Please give me some advice on how to handle this and how to deal with my in-laws from now on. Thank you.