Oh OP I feel you this was me when my DD was born. She was prem and I spent every single waking moment either feeding, expressing, or finger line feeding and doing exercises with her to try and help her speed up muscle development to feed properly.
Have you considered a hugabub or something similar? Just wearing your baby can help with milk production plus, he can feed while it in which is a huge plus!
Fenugreek is good for quick letdown, but it doesn't boost supply. It's also best to take in it's natural form, not tablet. So if you can get the seeds, take 1tbsp 3 times a day with water, don't chew.
But if your supply is low and compressions/massage isn't helping, you can try lactation cookies but if that doesn't help, motilium would be your best bet.
Good luck xx it's so stressful. Just remember, it's ok to mix feed. I know you want to BF but formula isn't the devil. I started mix feeding because my DD just wasn't putting on weight. Once she's put on weight and her stregth was up, she could BF a lot better.