If I am correct you are not getting normal flow, its just spotting and also you are planning to conceive.
Now because your period got delayed by 4 days so it is little early but the catch here is that you are getting spotting per vagina . Spotting can occur in early pregnancy
1. Urine pregnancy test. (UPT)
This can be done at home using commercially available urine pregnancy test kits available with the chemist. The instructions and result interpretations are mentioned in the kit itself. If it shows positive means you are pregnant and the spotting needs urgent management.
If the test shows negative then wait as it may be normal cycle.
Did you have irregular flow in the past as well?
2. Pelvic ultrasound
Even if your pregnancy test is positive or negative.
Let me explain how ultrasound is going to help: If your UPT is negative it would help in diagnosis of other gynaecological causes of irregular menstruation
plus since you have been planning for a year it would also help to rule out any PCOD
that might cause difficulty in conception.
If your UPT is positive then apart from diagnosing the site of pregnancy it would also visualize the site of bleeding.
Anyways I do not think this time the probability of pregnancy is high considering you are getting cramps and spotting only after 5 days of due date. But at the same time I suggest for evaluation because it would help in diagnosing the causes of difficult conception as well. I would also suggest that since you have been trying since a year , do see a Obstetrics and Gynaecology Doctor specialised in Infertility
for further management.
Do not worry these problems are very common nowadays and can be easily taken care of by specialist.