Be extremely careful. It’s too easy to be blindsided by, and end up rationalizing our sin.
Perhaps you have a health condition treatable with breast milk, and you’re considering finding a wet nurse, or nursing a sick man.
To do this without sinning, you need to head over to China or similar country, find a hospital that practices adult wet nursing for health benefits, with many safety protocols such as cameras in place, and a no contact below the waist policy, with all nursing taking place in full view of hospital administrators. The keyword is witnesses.
Anything less, and you won’t be avoiding the appearance of evil which 1 Thess. 5:22 warns us about.
If you can’t make it out to an Asian country where medical wet nursing might be a remote possibility, then surround yourself with many witnesses who can attest to the nonsexual nature of your nursing sessions.
Or you can seek expressed milk. Or just wait till marriage, thereby altogether avoiding the possibility of sinning against a holy God.
The more intimate you are with Christ, the more likely he’ll open your eyes to ways you’ve been blinded by your sin. He’ll get you right back on track.