Why can't I do this anymore and still sleep at night?

I’ve had a similar history, used to drink coffee into the evening, now have to take some melatonin to sleep through the night.

Part of it for me is a reflection of stress in my life – not anxious over anything but a lot of anxiety and stress, which is reflected in high blood pressure. That is symptomatic of high levels of cortisol, which disrupts sleep patterns.

Yep, what he said. ^^^
Last winter I stopped to order a Mocha on a cold late afternoon around 4:30 not even thinking about the possible effects of caffeine. I was awake until 4 a.m.! What a nightmare!
Yes, stress and anxiety, conscious or otherwise ramps up the cortisol and not only interrupts your sleep cycle but can cause weight gain as well. I take a benedryl to fall asleep myself.

@Coloma so this means that all those years as a teen and later on as a newly married woman I was not under stress?
I have a feeling that something else, something physiological is going on.

@Aster As we age we become more sensitized to many things. Allergens, drugs, drug interactions, alcohol, etc. I don’t think stress is the only issue, just that IF you are stressed and your Adrenal glands are producing excess Cortisol, that combined with sensitivity to caffeine can contribute to poor sleep. The sensitivity to caffeine alone is enough to ruin your sleep patterns. I too never used to have an issue so think it is mostly due to age related sensitivities.

Two and a half years ago I took a 10-day course of Amoxicillin successfully for Lyme disease. Six months ago, I started a similar course for an surgical-related abcess. After less than 48 hours, I broke out in fiercely itchy red raised welts from stem to stern. Yup. I am now allergic to that particular antibiotic.

Coffee is a deadly poison to human beings. It is called an alkaloid and is in the same alkaloid family as heroin and cocaine.
You had resistance to this poison in your youth, but no longer. It is part of the growth process and has absolutely nothing to do with stress.

@Dan_Lyons coffee also has potent antioxidant properties and has been linked to lower cancer risk and may be liver protective. It’s also been linked to a lowered risk for parkinsons and type 2 diabetes. Caffeine itself is thought to be responsible for some of this. I’m more sensitive to it now so I don’t drink it all day now, just a couple of cups a day. It is an alkaloid but not a poison in the amounts we consume.

I asked a question on here recently about the effects of caffeine at night. I am unable to find it now but will later unless someone else wants to now.

@jca You are probably a “slow metabolizer” of caffeine. It’s genetic. I am myself and I simply don’t have any after about 2:00.