How can my boyfriend be so careless?

We've been dating for about 8 months. Last week he told me that he would introduce me to his mom for the first time. I was so excited and prepared everything. I bought her flowers and some treats. He showed up to my house saying that his mom went out with her friends already and he forgot to tell me. I was so upset and kinda got mad at him. We still went to get dinner. I talked to him normal the whole time and tried to be understanding because things happens. He took me home right after dinner even it was still early. He said he felt tired and needed to go home and rest. He even offered to pay me back the money that i spent on the gifts for his mom. I rejected and asked if i can come and see her the next day. He said i can but he'll be sleeping, i can go talk to her myself. I got mad again, how could he be so careless? I don't speak Spanish and his mom doesn't speak English either. He said i can use sign language or he'll tell his mom to learn English. He looked mad too but i dont think i did anything wrong. What should i do about this? Thanks
How can my boyfriend be so careless?
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