Interesting situation and a post for help

Hey all, I'll describe the context first but in short the question is: do the probiotics BB-12 and LGG have something special about them, maybe in their production of SCFAs, in relation to severe, severe grogginess/lethargy?

So about two years ago I took the antibiotic doxycycline. I had horrible side effects, both physical and neurological, including feeling suicidal. I finished my course and haven't been the same since. For the longest time I couldn't digest anything. I had massive bloat and constipation, terrible anxiety, brain fog, panic attacks, and fatigue. I clearly was having malabsorption issues as well because my hair and skin became very dry and brittle. Sometimes I would have a week or two long stint of randomly fainting and heart palpitations.

I went to doctors, the ER, and such an inordinant amount of times throughout these two years. Blood tests always came back fine, heart monitor came back fine, ultrasounds on basically every organ came back fine, MRIs came back fine, a combined colonoscopy/endoscopy came back fine, and so on — every test came back normal. No h pylori or c diff, no parasites. I asked repeatedly for a SIBO test but was denied. I would plead to explore more since I'm so debilitated I can't work, often can barely stand, and sometimes have panic attacks so bad I fear what I'll do, but doctors shrug their shoulders and say something to the effect of "come back if it gets worse." I've historically been a healthy athletic individual so I've always eaten well. I've tried everything over these past two years, most recently being a two month antimicrobial protocol for SIBO. This helped somewhat, and was back and forth.

In the last two weeks, a lot of the digestion and anxiety/panic issues have greatly reduced. However now I feel completely groggy and tired to the point of feeling like I'm going to go into a coma. It's not just tired or even exhausted, but as if you had taken the max dose of a sleeping pill and then tried to stay awake, or the feeling when you just come out of anasthesia. You're groggy in a semi-conscious way; you don't feel like you're really "there." It feels somewhat like depersonalization or similar, and it freaks me the hell out.

Here's the interesting part. Having tried so many other things, I decided I'd try probiotics that have the most research toward positive effects on mental health, coming to the probiotics BB-12 and LGG. I have taken many pre/pro/postbiotics in the last two years to limited value, but targeting BB-12 and LGG has an actual effect. For an hour or so after taking around 10 billion units of both, the severe grogginess and lethargy goes down. Doesn't go away, but actually goes down in a way that feels like they are specifically targeting the issue. This does not happen with other probiotics, fiber, or dietary changes.

So what's happening? At the moment I'm wondering if my stomach isn't producing short chain fatty acids, and BB-12 and LGG are particularly helpful for me to produce them. But it's weird and I don't get why these two alone have this specific effect. It also goes away in an hour (maybe two), so to not feel like I'm going to go into a literal coma I have to pop these probiotic pills every hour.