am i over reacting?? or nah

So Weeks ago my SO's mother told me her friend's daughther is coming in our town for the holidays. She asked me if i could take her out sometimes and bring her out make her visit when i have time. Insaid of course doesnt bother me at all i love my SO's mother so much. So these past months i've been really tired cuz my SO and i work full time in his store. And sometimes we sleep very late and have to wake up early. Im a very sleepy person in the morning i have to fight myself to wake up 😂( sometimes) and lately my SO wont stop telling me : you sleep too much. Im tired of waking you up all the time (4times lol...) and you always wake up after 9. I dont have school for the moment and im always with him at his store. I told him look babe i know i wake up a 10 all the time but im tired! We never had a break together.. Well today i was supposed to go to the mall with the girl that came( she came yesterday) I texted her to meet and she told me shes already out with her friend. ( note i dont know her never saw her) i said okay. Them now i went on my SO's fcbk to ask my SO's brother if he could help me tmrw with something and i saw his previous messages with my SO. ( my phone was dead) my SO told him: tell her to come meet isis here so they can go out. Since she aint doing shit here she can atleast take care of the guest. I was pissed! Im the only person beside him that can help with the store. Every body else is too busy. I confronted him about it. And hes like : well i told you 1000 times u sleep too much I was fed up. Is that a reason? 😐 i still dont understand why talking about me like that to his little brother. I help because i want not because im forced to you know? What the hell