My period came on time this month but strangely, the period blood only comes out when i pee. The blood that flows out is red and thick like normal period blood. But, the problem is usually, i have heavy flow on day 2 and 3. But this time, the blood does not flow out much on my sanitary pad but quite a heavy flow only when i pee. This period is also shortened to 4 days instead of the normal 7 days I have. Is this normal and could it be implantation bleeding?