TTC Dilemma

Hubby and I️ are having a Dilemma. We have an 17 mths old son who still wakes up at least once in the middle of the night to nurse. I️ want to stop nursing so I️ can start trying to get pregnant again. And would love for our son to finally sleep through the entire night. Can anyone please help!! He stopped drinking from bottles at 10 months, and only drinks from straw cups or the 360 cups, never liked pacifiers, he started potty training and is going well. Why can’t he let go of the boob 😩 I’m in my 30s and hubby is 40 yrs old so I’d like another child ASAP.