It sounds like you're in a tough spot, and the changes you're describing are unfortunately common when someone continues using substances over time.
The initial euphoria you experienced when using stimulants (whether it's something like cocaine, meth, or prescription stimulants) is related to a huge surge in dopamine and other neurotransmitters in the brain. At first, these chemicals give you that "high" and boost your energy, but over time, your brain gets used to that level of stimulation. This means that the same dose will no longer give you the same effects, and you might find yourself needing more just to feel a fraction of what you once did. This can lead to a cycle of chasing those early highs, which might result in feeling more frustrated when they don't come back.
On top of that, stimulant use has serious effects on the body. The sleeplessness and increased heart rate you're experiencing are signals that your body is under stress. Stimulants can mess with your sleep cycle, making it hard to rest properly, which can worsen things like irritability, anxiety, and even depression. Your brain is essentially getting overwhelmed by the chemicals, and it might not be able to return to a balanced, healthy state without some time and support.
It’s also possible that tolerance has built up, so what once felt good now only gives you the negative side effects. The fact that you're not feeling happiness or euphoria anymore is actually a warning sign that your brain’s reward system is being overstretched by prolonged substance use. This could also explain why you're no longer finding the same pleasure in the things that used to excite you, which is a hallmark of something called "anhedonia."
If you're ready to take steps to turn this around, it’s really important to get the right support. Sometimes, people need help from healthcare professionals who can guide you through detox and recovery. Therapy, counseling, and support groups can help too by giving you the space to understand the roots of your substance use and find ways to regain your well-being.