WTF is wrong whid this engine

I have a problem i newer had to do whid before its a 98 honda civic aerodeck 1.5,it runs grate but whid the termostate in the engine theres no heat in the cab and if I remove it iv got all the heat i need,iv flucht the hole system and the waterpump is new as the termostate,no coolent is disapering and normal pressure in the system im pulling my hair

Are you putting the thermostat in backwards? Attach some photos, please.