Since this is a new symptom, I would notify my doctor if I were you. It could be benign, but it also could be an ulcer/gastric bleeding. The Victrelis side effects do not specifically state ulcer as a possible side effect, but they do indicate that gastric bleeding could be a side effect (black, tarry or bloody stools).
http://www.drugs.com/sfx/victrelis-side-effects.html
Side Effects of Victrelis - for the Consumer
Victrelis
All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Victrelis:
Change in taste; decreased appetite; diarrhea; dizziness; dry mouth; dry skin; hair loss; headache; irritability; joint pain; nausea; tiredness; trouble sleeping; vomiting; weakness.
Seek medical attention right away if any of these SEVERE side effects occur when using Victrelis:
Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); dark, tarry, or bloody stools; fainting; fast or irregular heartbeat; feeling cold, especially in the hands or feet; fever, chills, or sore throat; pale skin; severe or persistent dizziness; shortness of breath; unusual bruising or bleeding; unusual tiredness or weakness.
This is not a complete list of all side effects that may occur. If you have questions about side effects, contact your health care provider.
I am weak and when I walk upstairs or my husband parks in east overshoe and I have to walk a long distance, I get real short of breath and my abs feel like I've done 100 crunches. Also get stomach aches after I eat never know what's going to settle!