Can you tell what was your strategy?
When you start the game, first thing you do is take loans and build 25-odd galleys, enough that you can take out the Ottoman fleet and blockade their ports. In 1.8 Byzantium is very wealthy and you can easily afford the upkeep and pay back the loans.
Wait for Ottomans to take out Albania and attack Anatolian minors. With their army gone, declare war and block the strait. Siege Ottoman European provinces at your leisure. Take as many provinces as you want and can. It takes two or three wars to expel the Ottomans from Europe besides Edirne. Every time do the same thing, make sure you have enough galleys to block the strait and enough land forces to defeat a possible Ottoman garrison in Edirne (usually around 12k troops).
You can seek allies to help your cause, Poland is a good target. They may not Rival Ottomans which makes alliance difficult but don't worry, that happened in my game and everything turned out alright.
When you reclaim European provinces, the obvious next step is Anatolia. This takes a bit of luck since you will have around 17-19 forcelimit compared to Ottomans' ~29.
Before going to Anatolia, save up a lot of money. Should be easy for Byz but don't be afraid to take loans. Start the war by destroying their navy and blockading their ports. Wait until their WE gets sufficiently high and cross the strait. Spend all your money on troops, if you are half decent at this game you should be able to beat them (I have only 130 hours in the game and I did it). Since you control the strait it's not a big deal if you lose a battle or two, so long as you're the last man standing sooner or later you will win.
When you have neutralized the Ottoman army, focus on taking provinces on the Aegean coast, as many as you can. Specifically take the province south of Edirne so Ottomans will move their capital out. When you have one major victory in Anatolia and 4-5 provinces there, you have pretty much won. By the time you are halfway through Anatolia you will be by far the most powerful nation in the region and it's just nonstop steamrolling from there.
TL;DR spam galleys to block the strait.