Yeah, I know the heaviness you're talking about. I call it the "leaden feeling." It's like something inside my chest sinking down to my stomach.
I've had days like that too where I go from sad to silly and laughing to angry and crying and depressed. They suck.
There's not much we can do about these moods on our own. As much as I stick my toe in the water of therapy and then run, I always end up coming back because this thing doesn't go away on its own. In fact, there is evidence that it only worsens (moods become more entrenched, high low and rapid cycling) with time if untreated. And the earlier you start treating it, the better chance you have of leading a fulfilling life. Sure it won't be perfect, just like no "normal" people's lives are perfect. You won't be ecstatically happy after taking your meds. You'll still have some mood swings, but after getting a decent combo, you probably will have less and less of these out of control days and extreme depression. I'm on meds and have still been hypomanic for most of the last 14 days. Why? Don't have a perfect combo yet. Still, better than 3 weeks of mania in may '08 and depression from winter '07 through most of July '09. My creativity has been almost non-existent but for those 3 weeks and some scattered days for 2 freakin' years. My mood swings are definitely not worth it, although while in the middle of a good one I'm so ecstatic that I don't really care about the depression. Then it comes back and I go, "Oh yeah, this is why I need help." And I will ALWAYS need help.
I'm glad you're not suicidal or cutting. If you start to get that way, you will ask/go for help, right?
It's okay to feel lost. You don't need to have "the" answer right now. Just know that there are options and not all of them will take away your freedom. In fact, therapy and good meds can be very empowering. You start to feel like you have your brain back and that it's not controlling you any more. When first on meds it won't feel that way, but don't give up. The side effects of the ones that are right for you will wear off with time. (eg. I was aggressive/impulsive and driving dangerously admittedly when first on Wellbutrin, but that went away after a couple of weeks. It increased my energy and ability to function day to day and I still take it).
So, not to keep rambling, but the fact that you're on here suggests to me that you're starting to consider treatment and that's good. I know you don't want to have a problem and to just be "normal" but no one's normal. Even the people without brain chemistry problems have other issues like gambling or cheating or lying or overeating or self-image or explosive anger or conflict with family members, etc. etc. If everyone got help for their problems it would be a better world. I like to think I'll eventually be part of the solution by getting well.

And things will improve. The start of therapy and meds will probably be very stressful and you'll feel like giving up because you feel horrible at times. But don't. There is light at the end of the tunnel. And, no, it's not a train coming.

(I used to say that when people told me that. Bad me.

)