Medical issues should ALWAYS be addressed by a doctor FIRST. You use the internet only if your doctor have not been able to help you. When was the last time you had a physical? Gas, constipation, acid reflux are things you should be telling your doctor.
As for your feeling of weakness, it can be due to many things including medical conditions. Many people have this fallacy that since they never have been seriously ill in their youth, they will never have a serious problem. I assure you as you grow old and older, you WILL face many medical problems. If you are lucky, they will be none life threatening and easily treated. Furthermore, as you age, your body is going to decline in many areas including your ability to recover quickly.
35 is not exactly over the hill, but you are no spring chicken either. You do NOT have the body of a 25 year old anymore. That means you have to be careful to not only give your body enough time to recover, but also eat right and get enough sleep. Sleep is when your body does the majority of the repairs/healing. And just because you do martial art does not mean you can eat whatever you want in whatever quantity. As you age, you have to focus more and more on quality instead of quantity - this includes practicing your martial art, diet, exercise, and even how you work.
After you have gotten checked by your doctor and have been treated for your problems, you need to re-examine how you have been practicing martial art, exercising, eating and even work. I been in the software field for over 25 years and done it all including working 90 hours a week for 2 straight months. If I had not been very careful of my diet, workout schedules and managing my work loads, I probably would had burnt out long ago. Take for example, rest periods during your work hours: do you take them? The human body was not designed to be hunched over a computer screen for hours everyday. Sitting for long periods of time is very unhealthy and dangerous - it is one of the most common cause of Deep Vein Thrombosis (DVT) which kills people such as those who fly frequently and have to sit for long periods of time. I make sure I never sit for more than 30 minutes without standing up and take at least a 5 minute break. When you are sitting down, do you sit properly? Are you slouching? Because if you are, then you also cannot be breathing properly and that means you are suffocating your body; not to mention causing undue stress and over pressure on your organs in your abdomen.
You practice martial art, but do you apply anything from your art to your everyday life? If proper stance, breathing, posture, body mechanics is important in martial art, then it should be equally important in your everyday life. Don't just practice martial art, live it.