No diamonds in 20w16a

Me and my brother started a world and started in the snowy mountians biome.(sidenote, when i was seaching for plains i could not find any) but as we progress i have found NO diamonds. we have spent around 8 hours in the world and have yet to find any diamonds. i'm not sure if we are just incredibly unlucky but we have dug a 3x3 tunnel for around 150 blocks striaght and have found only iron, redstone and gold. and 1 block of lapiz, but have no diamonds. we wanted to visit the nether but without the diamonds to mine obsidian we cannot make a portal. we did find one in a chest at the wierd unfinished portal places while exploring but have only 1 block