Ok, so I looked at your dotabuff, and two of your three games appeared to be stomps where not much could be done, but one was quite long so I thought I'd give it a look.
I'm still gonna go through and try to see what tips I can give, but good lord, this is some deep trench you are in buddy. My sympathies. At least you buy wards when needed regardless of hero, it's a good habit.
Ok so I looked at the first 40 mins of this game
http://dotabuff.com/matches/727498846. My notes:
1. You went boots and a 4 tangoes as your starting items. On a carry like PL you should not be going boots first. It's only really viable when against a razor mid or on some offlaners or roaming supports (maybe some fringe cases I'm forgetting). Instead, get a stout shield to deal with the ranged harass you were likely to be up against, and were. Then I'd say tangoes and a salve.
2. Your lanes were awful. This obviously isn't all down to you, but did you ask legion to see if she would go jungle so you could farm the lane? As it was you let her farm and kinda stood around spamming a few lances, until you killed the small camp a couple of times. You had 2 possible supports top and 2 carries bot, not exactly efficient. This also meant you had like 5 last hits 7 mins in.
3. Camera control. To be blunt, yours sucks. I think I saw you move the camera away from your hero like 5 times in the whole 40 mins I saw. Constantly looking around the map to check enemy items, levels and health is very important. And whilst in lane, it's a good idea to keep both you and your opponents in view as much as possible. You often had it so your hero was right in the upper corner with empty space filling the rest of the screen. This way you can see nothing of what is going on in front of you beyond the wave.
4. You bought wards. Great! That's an improvement over everyone else there. But as a small note, you don't have to use all of them immediately. When you first bought 4 of them (I assume when you got too frustrated at no one else getting them), you placed all 4 straight away. One at top rune (good), one at bottom rune (also good), but then the other two were next to the lane and inside your jungle respectively. Think about what this achieves. The lane one arguably lets you see people wrap around the treeline, but a tinker and morph are not all that threatening in that respect, and they both stayed in sight of the creeps all the time anyway. The jungle ward was entirely useless. The bot rune ward would show you if qop was ever coming to gank, and all towers were up so there was no other entrance to your jungle. Hold onto those wards for when they are needed rather than wasting the 150 gold you spent.
5. So the game broke down, and eventually the fighting started. Towers were taken, laning ended. At this point, you had treads and a morbid mask. There was zero impact you could have on fights. So you need to make the decision to either try to fight anyway or abandon team and farm. As it was, you went to a lane, saw a fight going on one lane over, walked halfway there, then walked back after not doing anything. This happened at least a couple of times that I remember. This is being incredibly inefficient with your time. You were missing entire creep waves this way. As a carry, you need to always be on the lookout for free creeps. If you see a lane and no one is farming it, go there and hit creeps. If you push it out really far and don't feel safe rotate into the jungle and it will eventually push back, whether by hero or tower. Tp to empty lanes that get to your tower. Always be farming, unless your team has grouped for a specific objective.
That's all for now in terms of general play, hopefully this helps. On the item front, I don't know if this game was before you got those replies here, but Helm of Dom is not good on PL. If you need lifesteal, get vlads, as it gives mana regen and comes in the form of an aura that is good for pushing. With helm, lifesteal is an orb effect, so it does not stack with diffusal (I believe). I didn't get to the point where you bought it, but S&Y seems not so good on PL as well. You want to turn that Yasha into a manta style instead.
Take all this as friendly advice rather than criticism, and feel comfort in the fact that your positioning was better than a bunch of other players in that match.
Edit: I see you replied whilst I was writing this up. Don't give up on farming heroes! They can be very fun, it's just getting used to how you need to behave in certain roles.
