
Eren disappeared for a bit and Levi was worried, so in ch6 Eren appeared and wanted to have sex. so while having sex Eren said that he wanted Levi to come inside of him (something like that) and thats when Levi knew 'ah he wants to have my baby and leave' And then he saw Eren putting the butt plug and...Cause the thing is those 2 are mates, but because that other alpha told Eren he's still attracting people (and thats not supposed to happen) Eren thought that Levi was not he's true mate...

So Levi confronted Eren saying like he only wanted to have NN's L's baby. Eren told him that he wanted Levi's baby not L's because he wanted Levi to not be able to leave his side...because he is a fake make.
Then Levi showed him that the reason he's attracting people is because he is special and is overflowing with love....
and thats it
sorry if its too long

Maybe because he thinks eren its still obsessed with his alter ego L's ans its in love with hes persona and not himself, check out chapther 3 when levi get furious when eren calls him L, he doesnt want to compete with himself---
I didnt understand ch6.... can someone explain it to me.. >...<