noob help: I keep stalling out and failing to attack

Honestly, I think the campaign bred this bad habit into me. Most campaign maps either have no time limit and encourage you to clear out the whole map at a slow pace, or are defense holdout missions, or can be cheesed by micro-ing Kerrigan/Nova. The mission I found the hardest was Rite of Rak’shir because I had to consistently macro out units, and in the end I just went with massed void rays, so I didn’t even really learn my lesson lol.

Now, I have a hard time past the first 5 minutes. I get through my build order, then I just sorta… sit around. If my opponent harasses me, then I’ll just stay in base until I have 4 digits worth of resources, then panic build 5 starbays and a fusion core to rush BCs. That usually works against the AI but players, when I do vs players, will just build corruptors or whatever and then I’m a big pile of money in the sink, so I surrender

This is stupid. I’m being stupid. Help?