This is very common. I don't know how old you are but obviously the older you are it will take longer to recover. I had a quad bypass at age 41. I was back at work in 3 weeks and feeling totally normal by 3 months. However a friend's father had the same surgery and he is complaining of the same symptoms as yourself and this is 8 months later. But it will get better.
You have had major surgery and it takes a long time to fully recover. Seven months is
about half way there. After a year most people lose all the soreness and pains totally.
With regards to the tiredness, are you exercising to strenghen the heart ? like any
other muscle it needs exercise to get stronger. Just go for gentle walks, nothing strenuous and make sure you walk very slowly to begin with so the heart can gently
increase its speed. Gradually pick up your pace and don't walk like you are in a marathon. Walk the same route each day, about 30 mins, and each day make a note
how you feel at different points of the journey. You will then know if there are improvements or whether something is not quite right. As you get used to the walk,
you will notice how you are breathing much easier and becoming more fit.