I need Help on my SSTO Spaceplane

You got me curious so I decided to see what it would take to build a functional SSTO spaceplane. Here is my attempt: https://www.simplerockets.com/c/YoLQky/Semi-functional-SSTO-Spaceplane

• It is very heavy: 270,000 kg wet mass
• Its atmospheric stage is 4 jet engines with 2,300 kN that can burn full throttle for 2.7 minutes
• Jet engines get me to around 10 km with a surface velocity of 500 m/s
• Stage 2 delta-V is 4,381 m/s in a vacuum (although a little gets burnt getting off the runway)
• Gets to orbit with 900 m/s delta-V to spare

The autopilot is pretty dysfunctional, and this craft is not re-entry ready (it just burns up).

It might help if you were a little more specific. I am not an expert on SSTO space planes, but I understand they are notoriously challenging because you have to carry 100% of your propellant storage and engines with you into orbit. Additionally, jet engines, assuming you're using a mix of air breathing engines and rocket, don't get you to anywhere near the velocities or altitudes you need.
But unless you can be more specific than just not having enough thrust I'm not sure anybody is going to be able to help you. What kind of engines are you using? What are their specific impulses (at sea level and in vacuum)? What kind of fuels? What is the mass of your craft? What is the mass of your fuel (jet fuel and rocket fuel separately if you're using both)?
Better yet, upload your craft and share a link then people could actually take a look, see what you are trying to do, and give you some pointers.
Also you could try searching the craft other people have uploaded: https://www.simplerockets.com/Crafts/Search?q=ssto although be aware that many of the craft you'll find on the site have had there XML modified in ways that violates the realism of the game (i.e. they have engines that generate unrealistic amounts of thrust for the fuel they consume).