Am trying to concieve!!?

hey all have been ttc since end of january and so far no go, i already have 2 children and fell with them within 3 months am startin to feel a lil low as cant work out why im not pregnant yet as in the past it happened so easily!! everywhere i look isee pregnant people and i am pleased for these people but feel a lil disheartened for myself!! i rencently brought the clear blu fertility monitor and due to start using it by the 14th of this month!! i just hope that this works for me and improves my chances xx