There are several phenomena relevant to this general thing:
1) It's not unusual for libido to fall off, at least relative to the increased levels seen initially, some substantial number of weeks into a cycle. For example, it could happen at 8 weeks.
This wouldn't apply to you at only 1 week in.
2) A compound might be used which itself harms libido, particularly nandrolone, but you are not doing that. Regardless of what some say.
3) Estrogen levels may fall below the bottom end of the normal range, but that could not apply to you here unlesss you are using an AI without having mentioned it.
4) In some cases estrogen levels above the top end of normal reduce libido. It is possible that that is the case in your situation, but it wouldn't be my first bet, which is:
5) In some cases, there is a paradoxical response where increasing androgen levels at first increase libido, but beyond some point which varies between individuals, yet-further increase in androgen decreases libido.
It may be the case that the dose you are using -- which we cannot know what it is, as you don't specify mg/mL -- is beyond your personal limit for amount of androgen yielding good libido.