"immediately had experiences of my whole body buzzing, levitating, spinning etc,"When we begin to meditate either with the practice of stable attention or with the practice of momentary concentration, samadhi starts to develop. Concentration deepens. The mind engages across mutliple mind moments with breath, breath, breath, breath .... breath. Or it picks and lets go of various objects from across the sense doors - object, object, object .... object.
With this intial samadhi (or khanikka samadhi) comes the tendency of the mind to create tactile, visual, auditory and sometimes olfactory hallucinations. these hallucinations are to be ignored. If they are successfully ignored then samadhi deepns to a point where energy and relaxation are both developed. We have a stable easy mind that is also very sensitive to data it receives.
This is the point where the mind makes a flip from object to characteristics and eventually universal characteristics. From what you have written here my conclusion is that samadhi started to deepen for you but you havent mentioned a settling down of the mind and a dropping away of these hallucinations. Your samadhi was deep enough for fairly powerful hallucinations to show up that shows that you have innate talent.
It is in this depth of samadhi where the mind has worked through the hallucinatory phenomena and has settled down that insight opportunities start to appear. And this samadhi enables the gaining of the insight knowledges from these opportunities.
"pressure in my third eye / between the eyebrows that oscilates between very hot (almost painful) and also very blissful"
Pressure in the head region and pain/bliss accompanying this pressure is usually a sign of an imbalance between attention and awareness. A yogi usually powers attention as if they would poke at objects or torture them until they confess with their attention. This usually leads to such phenomena. My recommendation would be that you learn to rebalance the power between attention and awareness. Depower attention and become more sensitive and receptive to awareness and to the objects within awareness.
"I used to be able to go into Jhana or an altered state of consciousness (like feeling like im floating) at will and although this still happens once a week I can no longer do this at will"
Consider the arrow of attention. We have a sense that there is something called attention like an arrow with the arrow head pointed at an object and a sense of 'me' sitting at the nock end of that arrow. The stronger the power in attention, intially, the stronger te sense of a 'me'. This is a type of me making, my making or 'upadana' in pali. This means that one is basically making the meditation about themselves. Jhana on the other hand is a process of easing into experience of letting go of ownership of experience thereby reducing the me making, my making. So this upadana is completely antithetical to jhana. One does jhana obviously, its not one's brother or sister who is doing the jhana. But at the same time the more 'me' and 'mine' exists in the mind the less likely jhana becomes.
This is what I can offer by way of diagnosing your practice from what you have written here:
1. You havent written anything about the insight knowledges that lead to stream entry
2. You havent described the quality of mind that arises and takes nibbana as its object at stream entry
3. You are describing innate talent with samadhi practice with associated early hallucinations
4. You are describing an imbalance between attention and awareness leading to headpressure and stuff
A few questions I have:
1. Have you settled on a system of practice that you will follow?
2. Do you have clarity on long term goals and short term more immediate goals?
3. Do you have a skill map either explicit or sketchy that you will use to develop the skills needed to further deepen samadhi and start doing insight practices?
