My thoughts on what you experienced would be this:

Neck tension is typically linked to the fifth chakra, which is about honest communication, with yourself and others. It looks to me as though you figured out the cannabis might be inhibiting your progress, making you less authentic, so you decided to eschew it for a while and ground yourself in a chemically unaltered experience for a time. I have nothing against cannabis, by the way, but it is no cure-all. Even if it helps with some blockages or helps to restore balance at times, it can just as easily create blockages and push one to extremes when its use is mismanaged. I find the longer the span of time between use, the higher the state it allows you to ascend to, ESPECIALLY when you're engaged in mindfulness practice all along, fixing whatever problems you notice as they arise. So, to summarize, the movement from the neck upward was a sign that you were re-engaging in a more legitimate dialogue with yourself.

Heat in the chest, in my experience, means someone is directing focused attention toward me. It happens every time I speak publicly in front of a group of people. Rarely it happens at a distance, but that tends to only be the case when I am focused on that person, as well. I knew a woman in Australia who practiced Reiki and she was able to generate that feeling once. As you stated, it's best to simply let that sensation pass, as it simply is acknowledging that you are open to connecting with others in a meaningful way. I would also mention that I am no "master" of chakra energy. I use it more as a way of tracking down disturbances that need to be remedied rather than trying to manifest my energy in any way other than the most subtle and kindhearted ways possible. There are all sorts of people who have experimented with chakra manifestation and they tend to have pretty stern warnings for how misuse can cause all sorts of harm. The complexities of balancing and appropriately utilizing one's own energies is more than enough to occupy the average person for a lifetime.

As an asexual person, I couldn't hazard a guess on the pelvis sensation. Cannabis certainly made me more sexually aware of myself, and I can always tell when I am feeling sexually passionate, but since those energies have no "outlet," I can either masturbate or channel them into my third chakra and get a lot of work done or have a very intense workout. What I can say is that in my experience, sexuality is by far the most often inappropriate expression of energy that human beings regularly undertake. When people take the time to involve the third and fourth chakras in their sexual activity, the experience is far more powerful and fulfilling, but obviously not something to be squandered on some random person you pick up at a bar. Trivializing sex is a guaranteed way to ruin one's chance at Enlightenment. Anxiety usually means you're apprehensive about something, so maybe the examples I gave resonate with you, or perhaps it is something else. I've had terrible luck with dating, unfortunately, but luckily I'm great at extricating myself from bad relationships, so I guess it balances out. :) I tended to choose girlfriends based mainly on chemistry and whether they were physically attractive to me, so first and second chakra only, and my results are what you'd expect from that kind of connection. Our "evolution" into hooking up rather than courting was a significant step backwards for us as a species and all but guarantees people (women especially because they are predisposed toward expressing the second, fourth, and sixth chakras, while men are predisposed to expressing the first, third, fifth, and seventh) never get to experience the full range of love and therefore never see it as anything other than an emotion.

Again, I can only reference my own experience in these areas, and while there will be parallels, your path may diverge greatly from my own. Mindfulness is always the key to progress, however. Every fiber of your being wants to end its suffering, and it's always going to be reminding you of that when it experiences something within or around you that is out of balance, because as you know, you are intimately connected to your surroundings, so dusting or doing laundry is as important to your practice as meditation and knowledge of what your body is doing.

Wishing you all the best on walking your path!