I've been weightlifting for about a month now. I have two questions for you that I haven't found an answer for yet.
First how do I push myself completely without spotter? I feel like if I'm going all out I'm going to hold back if I think might need help.
How long should I pause between reps? If I have to wait 15 seconds between reps in a set am I trying to push too much weight?
Use a cage or rack for a spotter.
That's a long pause. You should crack out the reps unless you're doing 20 rep "breathing" exercises.