Subwoofers hitting very weak, how to increase?

I have a 2015 Honda civic that I just installed my Sony amp and alpine 10"s with a stock head unit. The amp is on the subs are on but the bass is very light. The stock radio doesn't allow me to control the bass, and the amp doesn't have any knobs on it to control. I d rather not buy a new radio and instal it.

"I d rather not buy a new radio and instal it.". That is the first thing you should have bought.

There are a lot of things that could be causing your problem, but to try to diagnose it w/o a lot more information would be impossible.
For starters, what brand/model amp? I have seen very few amps in the last 20 yrs or so without at least some basic controls. And specifically what subs (dual/single voice coils? 2, 4 ohm?)
How are you getting signal from the stock radio to the amp? High level amp inputs? Line output converter?

Generally, adding an amp and subs and/or speakers isn't a big deal with a stock radio. Getting signal from HU to amp is usually the main issue.

There could also be issues with wiring between amp and subs, or between the subs themselves.

Here, read this - http://www.crutchfield.com/S-IRHq5vnpvx6/learn/car/subwoofers/tuning.html

I have not seen a car radio in the last 45 years that didn't have a tone control. Some Hondas have a kind of automatic noise limiter built in them incorporating a microphone and automatic circuitry. Snoop your owner's manual to see how to adjust it if you have it.