Best tactics for 3-4-3

[Drewpell]

Level 6 manager playing 3-4-3 . DR-DC-DL , MR-MC-MC-ML, AMR-ST-AML. 100% overall best in the league, and losing matches or struggling everywhere. Curently playing Normal, both flanks, mixed passing, contra-attacks, low def, normal tackle, off-side trap off, zonal. The DC is my corner taker with SA. What am I doing wrong or what can I improve during matches ? What should I change when thing don't go my way? maybe at half time switch to 4-4-2 ?
PS: GK - 22y 87%, DR - 22y 98%, DC 19y- 105%, DL- 20y 99% SA wall, ML 18y 95%, MC 19 87% SA playmaker, MC 18 100%, MR 18 100%, AML 18y 96%, ST 20 110% SA freekick, AMR 18y 100%