Avenues to more senior level positions?

I feel like I'm at a bit stand still in my networking career and would like to get some advice on how to take it to the next level. What areas of networking should I be focusing on in particular if I want to get into more senior level positions or higher paying positions?

Just for a bit of background, I've been in networking for 3.5 years now. In this short period I've gotten my CCNA and CCNP Security certifications, all while spending every second of my workdays trying to soak up any new material I can fit in. I'm currently the sole network engineer for a 1000+ user enterprise network - managing all Cisco/Juniper switches and routers, VPN, firewall, CUCM/CUC, ISE, etc. I've also spent a great amount of time automating various network tasks with python and have built our internal industrial network from the ground up.

At the end of the day I feel like I'm underpaid for the work I do and my passion :( I was hoping someone may have advice or past experience on moving up the networking chain. Is it as simple as just applying to job after job and getting more experience? Are there any specific technologies that are sought after more in the market now? Any specific certs that would help in landing a next level job?

Thanks for reading and any input..