If you're looking for inexpensive mod, slightly more powerful than the ego, check these out...
Diamond Mods
Shine Mods
They're 3.7v with one batt configuration, or 6v with another, I think.
Those are some seriously cute mods for $25! I'd guess your batts are fading. I've used my ego happily for over a year now, and just starting to delve into some more powerful options. For me, I just want something a little stronger. But you may well try cleaning the threads inside the 510 connection with slightly damp cloth. I use witch hazel.. not sure if that's a good thing or a bad thing, but I wanted something slightly astringent. Also, you can always just buy new batts for ego. I get mine from HealthCabin... fortune to ship from china, but if you're stocking up on cartos (boge 5pack for $4.50) and other stuff at the same time you still save a ton, even with shipping. Liberty flights (w 20% off button) is another good option. Personally, i couldn't decide if I wanted a fixed voltage 5v or a vv, so everyone told me to try one of the cheap vv boxmods at madvapes ($35, but with charger and batts about $60). I put out a 'WTB' listing in the classifieds here, and some fabulous person sold me one of his VV boxes, charger and batts for just under what I would have paid for the box alone, so that's an option. But seriously, HIGHLY suggest one of those VV boxes. They're amazing, performance wise. I resisted just cause I'm not fond of the terrorist detonator look
but finally gave in, and the performance... whew! And you can find your vaping 'sweet spot', voltage wise, since they range from around 3v up over 6v. They don't HAVE to be horrible looking, either. I'm about half way thru decorating mine, and its pretty darned cute, actually. Good luck! Get a cheap vv box, satisfy your current cravings, and that'll help you decide where to go from here.