Two common sources of leak are bad "O" rings and leaking Schrader valve stems.
Since the compressor itself gets hot and adds more heat to the under hood environment, starting with "O" rings of the two hose connections to the compressor is a good and accessible starting point...ideally on the way to changing the other "O" rings.
While you still have refrigerant in the system do the "spit test" to both the low pressure port and the high pressure port to see if these valve stems are leaking. If the glob of spit (or soapy water) bubbles, you can try to tighten the valvestem with a small stem wrench...just like one does with a bicycle tore. DO NOT TRY to replace these valve stems as they can come out like a bullet. The system must be TOTALLY EMPTY to replace the valve stems unless you have special A/C tools and experience. Always wear goggles when fooling with A/C systems.!!!
Hopefully, some of the r134a that you used has the correct green fluorescent dye in it so that you can hopefully detect the leaking area(s) with a bright UV light and the accompanying enhancing goggles.
Ideally, you need to seen a Tech to properly service your system...and, add a new dryer canister.