"Flutters" or Gas?

So being the planner that I am, I am reading somewhere between 4-5 books on pregnancy right now. And in some of them it says you won't be able to start to feel the baby move until 16-20 weeks while in another book it describes "flutters" that can be felt as early as 13 weeks. Well, I am 13 weeks and 3 days, and today at work whenever I actually had a chance to sit down I started noticing a weird sensation right where the baby is, living right now. It almost feels like something is tickling me from the inside. It is just sweet. It's so faint and barely there. I am and always have been extremely in tune with my body, so I feel like it makes sense that I would feel the slightest movement as early as I can. The frustrating thing is, if you tell a doctor or any medical person for that matter about the sensation, most will tell you what you felt is gas. This, is not gas. I can only feel it when I am sitting or laying down and it is totally random. We all know what gas feels like and I am not an idiot. I am convinced its the baby and I am SUPER excited about it! I just wish I could feel more :) I don't want to wish away this pregnancy, because I know all of a sudden I will have an 18 year old and be planning graduation parties instead of baby showers but I am so excited for all the fun stuff to start happening!