Did you go safelane or solo offlane ? Offlane can be pretty unforgiving on him, but sometimes you can get doublekill out of the blue if they underestimate shukuchi and germinate, due to the way cooldown on it works, running away gives you bigger chance for it to be off CD so you hit really hard. Then the support gets a few levels and they can instantly nuke you down so you just fed 2 deaths and the rest of the team is yelling at you.
Rush to basi ASAP, the damage bonus is simply too good and then whatever you can afford, usually 1 defensive item like linken or bkb, you can even buy ring of health before boots or skip threads until you get the big items, however you should get them at some point. If you are having trouble surviving, naked vit booster is pretty good option. Vanguard/drums feel like wasted money to me. I usually wait with maxing swarm, it's a bit of a 1 point wonder and around that time you should be getting focused in teamfights a lot, so I just pump stats a bit, ever bit of hp counts until you can timelapse.