Acussing me of making excuses

So I was otp with my boyfriend and I told him that I was going to get my mom a cake for her birthday

And hes all like go ahead and hung up once I got into the store he texted me saying this

If you wanna make excuses for you to leave with your friends dont bring your mom to it

Just tell me yourself your going out with your friends and well go from there

And obviously I told him can you stop accusing me over that I told you I'm getting my mom a cake plus if you could've been on the phone with me everything would be fine

I'm still at the store I just wanna cry hella bad

I dont know what to do