I always feel heavy abdominal pain and bloating in my stomach. What is the cause for this symptoms? Is this also a sign of pregnancy?

Not always... There are lots of reasons for abdominal discomfort & bloating, & not all of them are due to the GI tract. Even "functional" syndromes may be present without underlying "disease." however PSBO (paralyzed gut) due to metabolic & inflammatory conditions nearby (like an untreated infection of the urinary tract) must be considered &addressed. Check with doctor for examination & the right treatment.