I've been using it for so long that I've just grown so accustomed to it, but I get that exact same heart pounding feeling. It's really strong for the first time I go back on cycle after 30 days off.
That's definitely not allergic reaction - you would have hives, redness, swelling, itching near injection site. It is possible to develop antibodies from the CJC1295 portion over long time use, which is why it's important to cycle off for a full 30 days after your cycle usage (30 to 90 days) which will help prevent that.
Generally won't run into those issues with Ipamorelin, but you will grow a tolerance to it and it needs to be cycled in same fashion.
If you run into any issues with sleep, you can pin first thing a.m. fasted, or anytime of the day really as long as you're following fasted guidelines.