Have had palpitations and tachycardia (up to 174 bpm). get very lightheaded, nauseous, weak and shaky. could this be svt?

SVT: it could be svt, hopefully you are seeing a doc so you can get diagnosis and treatment as appropriate

Yes: It's very possible that this is an SVT, they can be exacerbated by dehydration, pain, infection, caffeine, stress, etc, if so - you should have it seen by a cardiologist/ep and consideration towards an event/holter monitor for diagnosis.