You do not have the power to raise a son who is not sexist. If mothers had this power, sexism would have been over a long time ago. The power of the mother is a patriarchal lie (and notice how mothers are always blamed for any transgressions their children commit). It is very appealing to think that our sons won't be like that, we will 'raise them right' so that they won't be like that. But they will be like that. Maybe they won't think ironing is a 'woman's job' (my children have never even seen an iron haha) but they will be sexist in some way.
Your husband will have a much bigger impact on his ideas about masculinity and how to be a man in this society than you can, but even if your household is a Utopian model of equality, you can't control what is outside your front door. Once he gets older his peers will be his main teachers and he will inevitably be exposed to a huge amount of sexist media, including pornography. I know it sounds bleak, but you have to accept that you cannot fully protect him from this. Our sons will be forced into the masculinity box, brutalised by patriarchy and grow up to be sexists, to a greater or lesser degree. It's heartbreaking but true.
That doesn't mean we should throw up our hands in despair and say fuck it, because of course there are things we can do that might help a bit. These are some things I am doing / planning to do with my son (he's 18 months):
Read him books with female protagonists
Teach him to respect bodily autonomy (including his own - no forced kisses and hugs with relatives, no forced tickling)
No 'boys will be boys' nonsense
I consciously go out of my way to encourage praise any kindness or nurturing play in an effort to balance out other messages he'll be getting (obviously he plays all kinds of games and I praise him all the time, I just make a special effort to notice if he cuddles a doll or puts a teddy to bed or gives something to his sister)
Use female pronouns for animals and people when sex is unknown (e.g. 'the doctor' is always she - I know he will get plenty of reinforcement of the idea that doctors can be men elsewhere so I'm not worried about him getting the idea that he can't be a doctor)
When he gets older, encourage critical thinking about all media, point out sexism when we encounter it, talk to him about sex and relationships before the pornographers get to him, talk to him about pornography, try to make sure he is treated the same as his sister when it comes to helping around the house (tricky right now because he is not as physically capable as her), control media and internet access for as long as possible (no unsupervised internet browsing for a long time, obviously I'll work out the finer details of that at a later date).