I have been on my cycle too long but want to extend now until end of august to prevent loss

Started out 750 mg test
400 mg tren en 12 wks
weeks 6 to 12 winny 50 mg a day

next 4 wks just 250 mg test en
500 iu hcg every 5 days

now back to 500 mg test wk
300 m,g masteron wk
Question is does the body plateau from drugs as my body fat and vascularity is great but strengh going down.
DO I need to change drugs or up dose of same ones