I don't know if it's only my opinion, but teams with only 3 defenders are the more easy to beat...

if don't have 1 ST, is an illegal formation... so I don't understand how can u loose 3-0... (is not impossible but...) I will ask you thinking in a real 3-4-3...

so.. to do 3 goals I don't have the key for you, but sure will be with 4 defenders, 4-3-3 is what I use always..., you need goals so, go hard in attack.

but you can try 4-5-1 if your team is good in defense, and with his formation gives u problems... that with long passing, and counter....

good luck!