I'm playing a half-orc figher battle master in a long campaign, his weapon of choice is a greataxe. We are level 4, planning to go to level 15 or something. The rest of the party are two clerics, sorcerer, bard and rogue (with some magic as well). We can always take a feat in addition to ASI.

I am usually the only one to approach the enemy, the rest prefers to stay in the back if possible. RP-wise, my character tries to support and protect the rest, especially the rogue, and he is not afraid to be a frontliner and take some hits.

I took the Alert feat to somehow combat my DM's obsession with enemies getting surprise attacks outside of the initiative, to feel more proactive and to have a better chance of reaching the enemy before the rogue's turn.

I have no idea what to do next and in what order for my next feats. Tough for more HP as the only "tank"? Sentinel? Something else? I could use some advice as I really want this character to feel durable and competent in a battle.